Typesetting terminal apparatus having searching and merging features

Abstract

A typesetting terminal adapted for operating a photo typesetter includes a data processor with a plurality of peripheral devices coupled thereto, such as a keyboard, cathode ray tube display, cursor control and a plurality of tape transports. Information from the keyboard and selected tape transports is read into the data processor memory for access and display by the cathode ray tube and outputting to a further tape device. Desired information can be searched in the various input tapes for display, editing and combination with information derived from another input.

Claims

We claim:

1. A typesetting terminal system comprising:

first, second and third tape means receiving and adapted to impart motion to first, second and third recording tapes respectively, said tapes being capable of bearing digitally recorded information,

a data processor coupled to said first, second and third tape means, said data processor including memory means for storing information,

display means coupled to said memory means for displaying information in said memory means,

means for coupling information from a first of said tape means as recorded on a first of said tapes into said memory means for viewing of at least part of the information from the first of said tapes on said display means,

means for locating selected information on a second of said tapes, including means for operating the tape means receiving the second of said tapes to impart motion thereto and for positioning the said second of said tapes in response to location of the selected information,

means for coupling located information from the said second of said tapes into said memory means for simultaneous viewing in combination with information present on said display means from said first of said tapes,

manually operable means for adjusting information in said memory means with said data processor for attaining a desired presentation on said display means including the combination of information from the first and second tapes at an operator controlled cursor location in information from the first tape for said simultaneous viewing,

and means for outputting combined information from said memory means to a third of said tape means for recording on a third of said tapes.

2. The typesetting terminal system according to claim 1 wherein information stored on the second of said tapes is stored in operator controllable length groupings having a predetermined gap therebetween, said means for locating selected information including timing means for testing intervals between data when the second of said tapes is moving, and means for indexing the grouping according to the number of gaps detected.

3. The typesetting terminal system according to claim 1 wherein the information on the second of said tapes is stored by operator controllable length groupings wherein the grouping position is identified by a recorded symbol, said means for locating selected information including means for detecting the recorded symbol, and means for indexing the grouping according to the number of symbols detected.

4. The system according to claim 3 wherein said manually operable means includes keyboard means for entering information into a selected tape via said memory means, including entering a said recorded symbol to identify a stored grouping.

5. The typesetting terminal system according to claim 1 wherein said means for locating selected information on the second of said tapes locates such information by content including comparison of a search argument with information read from the second of said tapes.

6. The typesetting terminal system according to claim 5 wherein said means for locating selected information provides the comparison between the search argument and the information read from the second of said tapes one character at a time without regard to contiguity between characters until the search argument is consecutively discovered, said system having means for reverse reading information from said second of said tapes upon such discovery for comparing contiguous characters recorded on the said second of said tapes to indicate identity of comparison.

7. The typesetting terminal system according to claim 1 wherein the information on the second of said tapes is organized in variable length groupings and subgroupings individually selectable by said means for locating selected information.

8. A typesetting terminal system comprising:

a keyboard for entering alphanumeric characters into said system,

a display means including a cathode ray tube and character generator means coupled to said cathode ray tube for displaying alphanumeric characters on said cathode ray tube as selected by said keyboard,

said display means further including a cursor register for storing coordinates of a cursor indication, said cathode ray tube being responsive thereto for displaying a cursor relative to said alphanumeric characters,

joy stick control means operable to enter information into said cursor register for controlling the coordinates stored therein,

a plurality of tape transport input devices receiving tapes each comprising plural variable length multiple line records adapted for entrance into said system in combination with characters entered thereinto from said keyboard and from another of said tape transport input devices,

an output storage device,

a data processor connected to said keyboard, display means and input and output devices, said data processor including memory means for receiving and storing input information from said keyboard and input devices for accessing by said display means and display of input information by said display means,

means for entering into said system an input identifying a record contained in a selected one of said tapes,

means for causing transport of said tape for search of said record,

means for recognizing said record and for interrupting transport of said tape when said record is recognized,

means for entering at least a portion of said record into said memory means for access and display by said display means together with information theretofore stored by said memory means as inputted from another of said tape transport input devices and already displayed by said display means for combination with the information theretofore stored and displayed at a location identified by said cursor on said display means to provide a combined output stream,

and means for coupling the combined output stream information from said memory means into said output storage device adapting said output device to provide the input to a typesetter apparatus.

9. The typesetting terminal system according to claim 8 wherein each of the tapes received by said input devices comprises a magnetic tape having said plural records magnetically recorded thereon, said system further including a punched paper tape reader input device, and wherein said output storage device comprises a paper tape punch recording an output paper tape.

10. The typesetting terminal system according to claim 8 including a tape transport subsystem for operating said plurality of tape transport input devices, said subsystem including a second data processor provided with a control memory containing a plurality of subroutines for operating said tape transport input devices, including control of the movement thereof, coupling of information thereto and therefrom, and location of information therein including the transport of said tape for search of said record,

said second data processor being responsive to control by said terminal system for comparing commands from said terminal system with commands also located in said subsystem control memory for jumping to selected subroutine located in said control memory.

11. The typesetting terminal system according to claim 10 wherein said second data processor includes a data bus for addressing said control memory, a bus enable means for coupling the output of the control memory to said data bus for re-addressing the control memory to an address comprising a previous control memory word.

12. The typesetting terminal system according to claim 10 wherein said subsystem is provided with further memory means for storing commands and status information.

13. The system according to claim 8 including means for entering records into said tapes including symbols for identifying said records, wherein said input identifying a record comprises said symbol.

14. The system according to claim 8 including means for causing said cathode ray tube to provide a display portion on the screen thereof for reporting the operational status of said system.

15. A typesetting terminal system comprising:

a keyboard for entering alphanumeric characters into said system,

a display means including a cathode ray tube and character generator means coupled to said cathode ray tube for displaying alphanumeric characters on said cathode ray tube as selected by said keyboard,

said display means further including cursor generator means and a manual control therefor, said cathode ray tube being responsive to said manual control for displaying a cursor relative to said alphanumeric characters,

a plurality of tape transport input devices receiving tapes each comprising plural variable length records adapted for entrance into said system in combination with characters entered therinto from another tape and said keyboard,

an output storage device,

a data processor connected to said keyboard, display means and input and output devices, said data processor including memory means for receiving and storing input information from said keyboard and input devices for display by said display means,

means for inputting information from a first of said tapes as contained in a first tape transport input device into said memory means for viewing by said display means,

means for entering into said system an input identifying a record contained in the second of said tapes as contained in a second of said tape transport input devices,

means for serially searching the second of said tapes for recognizing the record thus identified,

means for inputting information as recognized on the second of said tapes into said memory means for combination with information theretofore stored in said memory means from the first of said tapes and displayed on said display means at the location in said information selected by the cursor positioned in the displayed information from the first of said tapes on said display means,

and means for coupling the thus combined stream of information from said memory means into said output storage device adapting said output device to provide the input to a typesetter apparatus.

16. A typesetting terminal system comprising:

a keyboard for entering alphanumeric characters into said system,

a cathode ray tube display means including character generator means for displaying alphanumeric characters as selected by said keyboard,

a plurality of memory input devices including serially recorded records including variable length records adapted for entrance into said system in combination with characters entered thereinto from another memory input device and said keyboard for display on said display means,

a data processor connected to said keyboard, display means and input devices, said data processor including memory means for receiving and storing input information from said keyboard and input devices for display by said display means,

operator controlled means for identifying on the face of said display means a location in said stored input information as displayed by said display means,

means for entering into said system an input identifying a said variable length record contained in one of said memory input devices and for causing serial reading of said one of said memory input devices for search of a variable length record thus identified for entry of said variable length record into said memory means under the control of said data processor and combination at said identified location with information theretofore stored in said memory means as derived from another memory input device and as displayed by said display means,

and means for coupling the thus combined stream of information from said memory means to provide an input to a typesetter apparatus.

Description

BACKGROUND OF THE INVENTION

This invention relates to a typesetting terminal apparatus, and more particularly to such an apparatus having improved searching and merging features.

Stand alone typesetting keyboards conventionally comprise a typewriter keyboard operating a paper tape punch which generates a paper tape used as an input for a separate typesetting apparatus, such as a photo typesetter. The keyboard may be provided with a hard copy typewriter or a cathode ray tube display and memory for viewing the information being composed. Such a keyboard apparatus may also be arranged to receive information from a paper tape or the like for correction or editing of the information on the keyboard. Systems of the foregoing type are very useful in composing and editing information, but lack speed and flexibility where large amounts of copy are involved. It may thus be desired to make extensive corrections in taped copy, or to make extensive insertions into taped copy wherein such information is located in another file. With the equipment available heretofore, such corrections, insertions or merging of information would be made by manually keyboarding the additional information or possibly by physically combining sections of paper tape.

SUMMARY OF THE INVENTION

According to the present invention, a typesetting terminal is provided with the ability for extensive file management and combination of files through the utilization of plural tape transport input devices from which designated information can be retrieved at will for viewing, editing merging and outputting in a common stream, e.g. to a common output device or tape, in final form. In the described embodiment, information is located on plural magnetic tapes according to groups called jobs and takes wherein the job is a major grouping and a take is a sub-grouping. For example, the chapters of a book may be identified as jobs and the paragraphs as takes. In the case of classified ads, classifications may be jobs and each ad a take. The operator may identify a particular job and take for viewing, editing and combining or merging with the main story or copy derived from another tape, and may quickly access the desired job and take without visually inspecting the extensive file of stored material. If the operator cannot identify the desired insert by job and take number, he may initiate a code search based upon selected characters recalled from the desired material. In this manner, vast storage capacity is provided to the system operator, but one which is rapidly usable for deriving the maximum and most efficient utilization of the apparatus and the operator's time.

Briefly, in accordance with an embodiment of the present invention, a typesetting terminal includes a keyboard for entering alpha numeric characters, a display means including cathode ray tube having character generator means and the cursor register for locating a cursor through which selected alpha numeric characters may be identified on the screen. A plurality of tape transport input devices contain tapes each comprising plural records, e.g., jobs and takes, adapted for entrance into the system in combination with other information such as may be entered thereinto from the keyboard or another tape. The system includes a data processor connected to the keyboard, the display means and input devices, the data processor having memory means for receiving and storing information from the keyboard and input devices, and for processing information for presentation by the display means. The operator can identify a particular record contained in a selected tape, and cause the searching of such tape for locating the record, after which at least a portion of the desired record is inserted into the processor memory for display on the cathode ray tube and selective coupling to an output device in combination with information theretofor inserted into processor memory, e.g., from a separate tape comprising the main stream of copy to be outputted.

It is accordingly an object of the present invention to provide an improved typesetting terminal system.

It is another object of the present invention to provide an improved typesetting terminal system having file management and merging capabilities wherein plural records are rapidly identifiable and may be combined or edited into a common output stream.

It is a further object to provide an improved typesetting terminal system having a large memory capacity.

It is a further object of the present invention to provide an improved typesetting terminal system wherein comparatively large blocks of information can be accessed as desired from a tape memory system, either on the numerical identification basis or on the basis of content and wherein the selected information can be manipulated and edited at will for combination in a common record.

It is a further object of the present invention, to provide an improved typesetting terminal system which is capable of handling large quantities of copy and is characterized by operator and equipment efficiency.

The subject matter which we regard as our invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings wherein like reference characters refer to like elements.

DRAWINGS

FIG. 1 is an over-all block diagram of a typesetting terminal system according to the present invention,

FIG. 2 is a block and schematic diagram of a portion of a cassette subsystem according to the present invention, particularly a processor portion thereof,

FIG. 3 is a block and schematic diagram of a further portion of a cassette subsystem according to the present invention particularly illustrating peripheral devices,

FIG. 4 is a flow diagram of command processing software logic employed with the typesetting terminal of FIG. 1,

FIGS. 5, 6 and 7 are flow diagrams of software routines further implementing the process shown in FIG. 4,

FIGS. 8 and 9 are diagrams illustrating steps in command processing sequences of FIG. 4,

FIGS. 10 and 11 are flow diagrams of software routines which translate input character data into a form utilized by the command executive of FIG. 4,

FIG. 12 is a flow diagram of a software routine which moves stored character data from a main memory storage area to a register area of main memory,

FIG. 13 is a flow diagram of a software routine which moves stored character data from the scroll memory area in main memory to a register area of main memory,

FIG. 14 is a flow diagram of a software routine which allows the system operator to interrupt processing by striking a key on the keyboard,

FIG. 15 is a flow diagram of programming logic which allows the operator to terminate processing during any routine,

FIG. 16 is a flow diagram of a software subroutine which obtains character data from a paper tape reader or cassette subsystem,

FIG. 17 is a flow diagram of a software subroutine which transmits character data to a paper tape perforator or cassette subsystem,

FIG. 18 is a diagram of a logical format for data stored on magnetic tapes,

FIG. 19 is a flow diagram of a software routine which commands the cassette subsystem to perform a rewind,

FIG. 20 is a diagram of a physical format for data stored on magnetic tapes,

FIG. 21 is a diagram of a block transfer operation,

FIG. 22 is a diagram of successful and unsuccessful code searches,

FIG. 23 is a flow diagram of a software routine for searching strings of character codes to find a defined word or phrase,

FIG. 24 is a flow diagram of a software routine which commands the cassette subsystem to move the magnetic tape to a defined position,

FIG. 25 is a flow diagram of a software routine which establishes the position in the scroll memory where input data is to be inserted,

FIG. 26 is a flow diagram of a software routine which checks operator keystroke commands for proper syntax and commands the initialization of hardware devices assigned for input or output,

FIG. 27 is a flow diagram of a software routine which controls the sequence of input and output of data from and to peripheral devices,

FIG. 28 is a diagram of command processing system sources and states and of state action procedures,

FIG. 29a to FIG. 29h are diagrams of EXECU action procedures shown in FIG. 28 and of keystroke action procedures to which EXECU procedures are linked,

FIG. 30 is a flow diagram of a cassette subsystem routine which continuously tests for commands from the main system, initializes cassette operations, and calls cassette subsystem subroutines,

FIGS. 31 and 32 are flow diagrams of cassette sybsystem subroutines which control movement, positioning, writing on and reading from magnetic tapes,

FIG. 33 is a flow diagram of a cassette subsystem subroutine which directs rewind and positioning of magnetic tape units,

FIG. 34 is a flow diagram of cassette subsystem subroutines which direct operation of a magnetic tape unit during tape positioning operations, and

FIG. 35 is a flow diagram of a cassette subsystem subroutine which posts the status of the cassette subsystem after each commanded operation is performed.

DETAILED DESCRIPTION

General System

Referring to FIG. 1, the terminal apparatus according to the present invention includes a central processor unit 10 employed in conjunction with random access memory 12, forming a digital computer configuration. In the particular embodiment described, the unit 10 comprises an Intel Model 8008 eight bit parallel central processor unit of integrated circuit form manufactured by Intel Corp., Santa Clara, California. The random access memory is suitably of the semiconductor type and may also be provided with a read only memory (not shown) for initial loading purposes.

The terminal according to the present invention further includes a plurality of peripheral input/output units coupled in parallel to central processor unit 10 and memory 12 via a parallel bus 14 comprising a plurality of data and address lines interconnecting the various peripheral units. Each peripheral unit is connected to the bus via an interface which provides buffering and/or coupling to and from the parallel digital bus coding either from an analog input and/or output, or from a serial or parallel digital source. The various peripheral units include the keyboard 16, a track ball or joy stick 18, a magnetic tape cassette subsystem 20, a paper tape reader 22, a paper tape perforator 24, and cathode ray tube system generally indicated at 26. The keyboard comprises a conventional typewriter keyboard providing means for inputting alphanumeric characters and/or other codings, as well as a control keyboard for initiating various control and editing functions as hereinafter more fully indicated. The keyboard interface and buffer 28 translates key strokes or series of key strokes into digital words which may be addressed on bus 14 for bringing about a desired output and/or visual presentation via the cathode ray tube system 26. The track ball or joy stick 18 delivers two dimensional address information for the presentation of the marking cursor upon the screen of cathode ray tube 32 in system 26. The location of the coordinate position for such cursor is transformed from analog form to digital form by track ball interface 30 and information as to the cursor position is subsequently stored in cursor register 34 in system 26 for presentation on the cathode ray tube screen. The location of the cursor mark on the face of the cathode ray tube is also available to the central processor unit for identification of the particular character adjacent to the cursor also viewed on the screen of the cathode ray tube. Joy stick systems for identifying a character with a cursor are well known.

Cassette subsystem 20 as hereinafter more fully described provides storage of information and access to and from information as recorded on a plurality of magnetic tapes, e.g. magnetic tape cassettes which are easily transportable from place to place and which may be inserted in or withdrawn from the system. In the specific embodiment, three magnetic tape cassette transports are included, e.g. one cassette from which information is being read to the screen of cathode ray tube 32, a second cassette to which information is being outputted and a third cassette from which insertions are made into the stream of information viewed on the cathode ray tube screen and outputted to the second cassette. Various combinations of inputting, outputting and merging of information via tape transport systems are possible in accordance with the present invention.

The cassette subsystem employs its own processor circuitry as hereinafter more fully described in connection with FIGS. 2 and 3, and this system is buffered into the main bus 14 by way of cassette subsystem interface 36. The cassette subsystem interface includes buffer register means and status register means through which the central processor unit 10 and memory 12 communicate with cassette subsystem 20.

In addition to magnetic tape transport means for the inputting of and outputting of information, the system according to the present invention also preferably includes the paper tape reader 22 and paper tape perforator 24, both of standard construction, which communicate with main bus 14 via reader interface 38 and perforator interface 40 respectively. Under the control of central processor unit 10, as programmed, nearly any combination of magnetic tape or paper tape input and output can be selected. The reader interface 38 stores information read in parallel form by reader 22 for application in parallel form to bus 14, and perforator interface 40 stores the information received in parallel form for parallel operation of perforator 24. The cathode ray tube system 26 communicates with main bus 14 by way of CRT interface 42. Information for display on the screen of cathode ray tube 42 is received in parallel a word at a time from random access memory 12 under the control of the central processor unit, and such information is stored via sub-bus 44 to refresh memory 46.

The refresh memory 46 cyclically applies digital information to D to A converter and character generator 48 by way of sub-bus 44. D to A converter and character generator 48 converts the digital information to analog values for generating cathode ray tube deflection and intensity signals in vertical deflection circuit 52, horizontal deflection circuit 54 and video amplifier 56. A standard character generator circuit is suitably included in circuit 48 for bringing about the generation of the correct deflection and intensity signals to portray alphanumeric characters on the cathode ray tube screen in the usual manner. As hereinbefore mentioned, position of a cursor mark is stored in cursor register 34 which periodically supplies coordinate information relative to cursor position to the D to A converter and character generator whereby such cursor is displayed at its proper location in the course of the deflection of the electron beam of cathode ray tube 32. Timing generator 58 synchronizes a general raster scan by the cathode ray tube, and at the same time coordinates the operation of refresh memory 46, D to A converter and character generator 48, cursor register 34 and video amplifier 56 so that desired information is cyclically available and displayed on the screen of cathode ray tube 32. The cyclic representation of information provides the viewer with the impression of a continuous display of the desired information.

As hereinbefore indicated, the information to be displayed is stored in random access memory 12 and is coupled via CRT interface 42 to refresh memory 46. A section of random access memory 12, termed a "scroll memory," can be addressed and new information stored for changing the display which will be viewed on the cathode ray tube. The scroll memory has greater storage capacity than the CRT's refresh memory and the scroll memory includes a buffer with the latter acting as a kind of viewing "window" into the information stored in the scroll memory. In response to commands scroll up and scroll down, changing portions of information from the scroll memory are applied to the refresh memory, giving the impression of moving a viewing "window" along the scroll, or winding the scroll relative to such window. The selection of the information viewed is controlled by timing an active period during which the CRT interface 42 couples information from the scroll memory into the refresh memory.

Relatively standard circuitry is utilized in the cathode ray tube system as well as in the other peripheral elements such as the joy stick, paper tape reader, and perforator, as well as in the interface buffering equipment, and has been heretofore available for typesetting function wherein the paper tape produced by the perforator is utilized as an input element for operating a phototypesetter. One such equipment comprises an "Ultracomp" terminal Model 808, 810 or 812 manufactured by Automix Keyboards, Inc., Redmond, Washington. However, the prior equipment did not include apparatus for file management, file searching, file merging, etc. employing the plurality of internally addressable tape transports. The following description is particularly directed to these features.

Cassette Subsystem

Referring to FIGS. 2 and 3, illustrating the cassette subsystem in greater detail, a bus connection to the cassette subsystem interface includes a data bus 60, an address bus 62, a cycle bus 64, and a test lead 66. The cassette subsystem itself includes its own microprocessor which is in general illustrated in FIG. 2 and a number of peripheral units illustrated in FIG. 3 which are joined to the same data bus 60 and in one instance to address bus 62. The microprocessor of FIG. 2 includes a program counter 68 addressable from data bus 60 and having coupled thereto a load enable connection 70 from or gate 72. The program counter 68 is employed to address a read only memory 74 which provides 256 bytes of selectable information on bus 76 to instruction/address register 78, compare gates 81, and bus enable devices 82. The compare gates 81 comprise eight exclusive or gates employed for comparing, on command, eight bits of information on the data bus with the selected output of the read only memory 74. The bus enable circuitry 82 comprises tri-state drivers for coupling the output of the read only memory to the data bus. Instruction/address register 78 stores a word from the read only memory, utilizing three bits of the same as an instruction applied to instruction decoder 80, the latter consisting of a binary to single line converter interpreting the instruction as one of the following:

Jh: jump high (jump if test is high)

Jl: jump low (jump if test is low)

Cmpi: compare immediate

Sti: store immediate

Lopc: load program counter

Co: control

Lda: load register A (from an address)

Sta: store register A (to an address)

The bus enable circuitry is operated via or gate 84 from instructions JH, JL or STI. An address portion of the word stored in instruction/address register 78 is applied to the address bus 62 by way of bus 86. Some of the addresses are applied to address decoder 88 by way of bus 90 wherein the number of addresses are decoded to single lines numbered 20 through 27 in FIG. 2 for indicating various peripheral devices hereinafter described in connection with FIG. 3. The address may alternatively select a data selector 92 which receives a plurality of indications from peripheral equipment in FIG. 3 as follows:

Dx: delay expired

Eot: end of tape

Rdt: read data present

Wre: write register empty

Cl: cassette loaded

Wp: write permit

Fcp: flux changes present

If a test is selected by an address to data selector 92 and such test is true, then test lead 66 will so indicate and provide an output signal for application to exclusive or gate 94 in the program counter jump circuit.

It will be recalled the instruction JH requires a jump if the test is high, while the instruction JL requires a jump if the test is low. Exclusive or gate 94 compares the level of test lead 66 with the instruction JL, it being understood that JH or JL are present in the alternative whereby only the JL instruction need be applied to gate 94. If either JH or JL are present, latch 100 is set by means of or gate 96, and then as the latch is clocked (by means not shown), the data input from gate 94, indicating the presence of a comparison, will appear at output lead 102 of latch 100 for operating or gate 72 in conjunction with instruction LOPC (load program counter).

Another input to data selector 92 is derived from latch 104 operated from compare gates 81 when enabled by instruction CMPI (compare immediate) from instruction decoder 80. When the output of read only memory 74 compares with data on data bus 60, and latch 104 has been set by the instruction CMPI, data selector 92 will supply a true indication on test lead 66.

For operation of peripheral equipment as well as data selector 92, use is made of four operating cycles as follows:

1. (DI): data in, gate 108 output low, gate 110 output low

2. (DO): data out, gate 108 output low, gate 110 output high

3. (JUMP): gate 103 output high, gate 110 output low

4. (CONTROL): gate 108 output high, gate 110 output high

These cycle indications are provided on four lines from cycle decoder 106, the input of which is connected to two lead cycle bus 64. Or gates 108 and 110 generate the binary indication of the cycle as indicated above in response to the instructions JH, JL, STI, CO and STA coupled as illustrated. It will be noted that data selector 92 is operational in cycle 3 while various of the peripheral equipment illustrated in FIG. 3 are indicated as operational during one of the cycles 1, 2 or 4 by a cycle lead applied thereto together with one or more of the two-digit addresses from address decoder 88.

Referring to FIG. 3, the following devices are seen to be coupled in parallel to data bus 60: tape unit select register 112, motion control register 114, interval timer 116, write register 118 and read register 120. Through the data bus, various words of information are coupled to a particular unit as addressed by one of the double digit addresses from the decoder 88 in FIG. 2, during cycle 1 in the case of read register 120 and during cycle 2 with respect to units 112, 114 and 116. Write register 118 functions during cycles 2 and 4.

The tape unit select register receives a digital word for indicating which of tape transports 122, 124 or 126 is selected for operation, and for energizing such unit. Motion control register 114 receives data regarding the direction of motion of the selected tape transport, i.e., forward and reverse, as well as regarding the desired speed of the tape transport. Signals are generated in motion control register 114 in response to the desired speed for operating speed control multivibrators 128 and 130, wherein multivibrator 128 is operable for controlling a tape speed of 10 inches per second while multivibrator 130 is operative to control a tape speed of 40 inches per second. The multivibrators receive second signals from read-write amplifiers 132, 134 and 136 associated with the respective tape transports, which signals are derived from a tape clock track for resetting multivibrators 128 and 130 appropriately when the tape is running at proper speed. The outputs of the multivibrators are connected to speed control circuit 138 via or gate 140 for bringing about servoing of the selected tape transports to the desired speed. Motion control register 114 also supplies a reset signal (RES) for resetting the selected tape transport to an initial condition. It is noted that the respective tape transports 122, 124 and 126 supply auxiliary outputs for indicating end of tape (EOT), cassette loaded (CL) and write permit (WP) indicative of the tab condition of the cassette. These signal indications for the selected tape transport are supplied to data selector 92 in FIG. 2.

Information is written into the selected tape transport by way of write register 118. The word to be recorded on tape is received in parallel form from data bus 60. Write register 118 comprises a shift register for shifting the information out in serial form to coder 142 where it generates the desired coding, e.g. bi-phase-level, for application to a particular read-write amplifier. For writing into the write register, address 22 is applied during cycle 2, while for serial writing of the shift register into coder 142, address 25 is applied in cycle 4. The write register also supplies a signal to data selector 92, namely WRE (write register empty).

For reading a tape, read register 120 and associated equipment are selected by address 24 during cycle 1. The information read from such tape passes through decoder 144 where it is converted to conventional digital format, and applied to serial to parallel converter 146.

From converter 146 the data is coupled in parallel fashion to read register 120 where the same is available to data bus 60. Address 24 during cycle 1 places the word on the data bus. A flux change deflector 148 is coupled to decoder 144 for indicating the presence of recorded information, and a latch 150 is set by serial to parallel converter 146 when a word is present. Elements 148 and 150 respectively provide the signals FCP (flux changes present) and RDP (read data present) to data selector 92.

Interval timer 116 receives the value of a particular time interval from data bus 60 when addressed by address 20 during cycle 2. The timer "times out" the period which has been entered, and supplies a signal DX (delay expired) to data selector 92 at the end of such period.

The A register 152 both receives information and supplies information to data bus 60. It is used as an accumulator when operated by an instruction LDA (load register A from an address) or STA (store register A to an address). The A register is frequently employed, for temporarily holding information, and in conjunction with a scratch pad memory array 154, hereinafter more fully described. Data entered into A register 152 is coupled via summer 156 wherein the data input may be incremented or decremented by adding one or subtracting one from the A register input as it passes through the summer, if the summer is appropriately addressed by a two digit address during cycle 4. Otherwise, data is entered into the A register without alteration.

Similarly, data may be entered into scratch pad memory array 154 from data bus 60, and may be retrieved from the scratch pad memory array back onto bus 60 through buffers 160 and tri state drivers 158. The scratch pad memory array is addressed via address bus 62 from instruction/address register 78 in FIG. 2 to select a particular register in the scratch pad memory array. The scratch pad memory array comprises a plurality of registers, for example 16 such registers, which are capable of selectively receiving parallel, eight bit words from data bus 60 during cycle 2 when an appropriate digit is received from the address bus by nand gate 162. When data is to be retrieved from the scratch pad memory array, the appropriate digit on address bus 62 operates nand gate 161 during cycle 1 which energizes tri state drivers 158 to place information from the addressed register in the scratch pad memory array upon the data bus.

GENERAL OPERATION

The terminal apparatus, according to the present invention, has for its purpose the generation of magnetic and/or paper tape which is then utilized as an input to a self-contained typesetting apparatus at a second location, e.g. a photo-typesetter. The operator of the terminal apparatus may compose and/or edit copy which appears in the form of an image on the screen of cathode ray tube 32 in FIG. 1, and which is then selectably included as an output, either on paper tape, via perforator 24, or on magnetic tape via cassette subsystem 20. When the operator views the copy on the face of cathode ray tube 32, certain conventional editing functions can be performed, such as the deletion of a character or word, or the insertion of additional material with the keyboard at a position selected by track ball or joy stick 18. In addition, a block of material may be selected and repositioned under the control of the operator as he views the copy on the face of the cathode ray tube.

Features, according to the present invention, include the management of files, e.g. as recorded on plural cassettes, searching for a particular file by identification number or content, and merging of information from plural tape searches into a common stream or tape outlet. For instance, an insert may be made to a selected portion of the cathode ray tube screen not only from the keyboard but from any location of any selected tape which can be designated by the operator. Thus, the operator may wish to type information up to a given point, or derive information from a tape input up to a given point, after which an insert may be selected from another tape and positioned, under operator control, at a desired location indexed for outputting in a continuous, merged and edited stream. In this way, a desired output tape for application to a photo-typesetter or the like, can be quickly composed in the final form while viewing such information on the face of the cathode ray tube.

To identify information contained on the plurality of tapes for selection at will, the material on the tapes is divided into groupings. Two groupings are used. The major grouping is called a JOB, and the minor grouping is called a TAKE. Thus, a job will include a plurality of takes. The lengths of groupings are determined as desired by the operator in the initial recording process of the tapes, wherein such recording may suitably take place via the keyboard of the present apparatus, or via a similar typesetting keyboard, terminal or the like. The manipulation of the data is software controlled by the central processing unit as hereinafter more fully described.

As hereinbefore indicated, important functions of the present invention relate to the searching of information in, and merging of information from, multiple input devices for selective viewing and possible editing on a cathode ray tube screen, together with outputting to selectable storage devices. The searching aspect typically involves a "take search," a "job search" or a "code search." In the instance of a job search, a particular numbered job and a particular designated tape transport may be searched in either direction. From the standpoint of the central processor unit, the operator designates the job number he is interested in locating, and such job number is stored at a memory location in random access memory 12. Random access memory 12 operates to register the particular job number and take number then being read or readable from each tape transport connected into the system, so when a particular job or take is designated by the operator, the job register in the main memory 12 is compared in central processor unit 10 with the desired job number as also inserted in memory 12, and motion is imparted to this selected tape transport until that job is found. The job may be inserted to the screen at a desired location. Under the control of the operator, the selected tape information is read into the scroll memory location within main memory 12 for coupling via interface 42 to refresh memory 46 whereby this information will appear on the screen of the cathode ray tube 32. This information may be inputted to the location of a cursor located in previous information on the cathode ray tube display and scroll memory, controlled by track ball or joy stick 18, and the information thereby merged with other information for outputting. The manner in which the function is implemented in the cassette subsystem is hereinafter more fully described. From the standpoint of the central processor unit, a similar operation occurs in the case of a "take search." The operator selects the desired take number and the particular job within which the take occurs, and such information is stored in main memory 12 for comparison with the information, also registered in the main memory, as to the job and take currently read or readable from a selected tape. The selected tape is then transported until in position for delivering the particular take to bus 14. Under the control of the operator, the selected tape may be read into the scroll memory location within main memory 12 for coupling via interface 42 to refresh memory 46 whereby this information will appear on the screen of cathode ray tube 32. This information may be inputted to the location of a cursor in the cathode ray tube display, controlled by track ball or joy stick 18, and the said information merged with other information above the cursor previously stored in the scroll memory for outputting as a continuous stream to a selected tape. Alternatively, information may be inputted to the screen, and outputted, if desired, up to the record being searched for.

The operator may have no record of the particular job and take where desired information is to be found, but may recall a starting code word or other identifying designation which would locate the desired job, take or sub-group. In such case, the operator would type in a "search argument" which is stored in a target buffer region of main memory 12. Blocks of information are read, e.g. from the cassette sub-system, and this information is read into the scroll memory portion of main memory 12. Then, in the particular embodiment, the "window" or buffer of the scroll memory selected for coupling to refresh memory 46 is inputted with information being searched, and characters appear on the screen of the cathode ray tube starting at the bottom line. As each line is formed, it moves upwardly or is scrolled up and characters are compared as they come onto the bottom line of the screen with the search argument stored in the target buffer. Comparison is made by the central processor unit. When a favorable comparison is reached, the process is stopped with the cursor in position at the point of comparison. As hereinafter more fully described in connection with the system software, the individual characters of the search argument are consecutively searched one at a time to ascertain their consecutive presence in the text being searched, but without regard to contiguity. Thus, if one were searching for the word TYPE the letters are searched in the incoming information without regard to whether the letters T, Y, P, E appear contiguously in one word. After all four letters have consecutively been found, a reverse search is made to see whether these letters are contiguous and if so the search routine is terminated. As in the case with the job search and take search, the thus identified information can be inserted at a location selected by the cursor and the data stored into the scroll memory, and may be outputted as a contiguous stream to a selected tape transport, e.g. with the information searched for immediately following the information theretofore inputted to the screen. The information as viewed on the screen may be corrected, edited or rearranged in a conventional manner before being outputted to a tape for application in operating a photo-typesetter or the like.

Turning to the general operation of the cassette subsystem, a particular command such as rewind, take search, job search forward, job search reverse, record a record or write a record is inserted by the central processing unit into the cassette subsystem interface 36. In an initial condition, program counter 68 in FIG. 2 addresses control rom 74 to place a word or byte in instruction/address register 78 which addresses the register in the cassette subsystem interface via bus 62 which may contain a command. The processor continues to ask the interface whether a command is present until test line 66 from the interface returns an indication that a command is present. Until such a command is found, the program counter 68 jumps back and continues making the inquiry. When the command is detected, the program will "fall through" to another section for placing the command code from the interface onto data bus 60. This command code from data bus 60 is first placed in A register 152 where it is "accumulated," after which the same is transfered to a register in scratch pad memory 154 under the control of control rom 74.

After the command is located in a particular register in scratch pad memory array 154, the program counter 68 and rom 74 go through a series of steps which compares the word stored in the scratch pad with successive words stored in the rom, executing the continuous cycle as hereinafter indicated in FIG. 30 with reference to the cassette subsystem program. A CMPI instruction from decoder 80 enables latch 104, and successive words in rom 74, selected as program counter 68 counts, are compared by compare gates 81 via data bus 60 with the command now stored in the scratch pad. A compare immediate instruction implies a second word or byte that has some data. The instruction splits off an address delivered to bus 86 which addresses the scratch pad location of the command, and the instruction portion (CMPI) of the same byte is applied to decoder 80 "turning on" the compare gates. The program counter steps another step, causing the rom 74 to present a command word for comparison in compare gates 81 with the command word residing in the scratch pad. If a comparison is produced indicating the command in rom 74 equals the command in the scratch pad, then latch 104 provides a compare equal output to data selector 92. Data selector 92 is addressed while a jump instruction from decoder 80 energizes bus enable drivers 82 via gate 84. Data selector 92 provides a jump indication on test lead 66 causing latch 100 to provide a jump command on lead 70 whereby program counter 68 then jumps to a next rom word enabled onto the data bus by drivers 82. Therefore, if a comparison has occurred between a rom word and a command word in scratch pad memory, a following rom word becomes the next address to which the program counter goes. In essence, a subroutine is accessed. As a result, the program counter will then step through a number of further instructions in the rom memory, starting with the instruction jumped to, whereby a subroutine such as read-write, rewind, forward job search, etc., will be executed as hereinafter described in the section of the specification regarding the cassette subsystem program. It is seen the rom 74 contains a collection of subroutines waiting to be used, and which are selected by a jump to such subroutine.

As indicated above, the instruction CMPI (compare immediate) is a two byte instruction. Other instructions which require two bytes to complete are STI (store immediate), JH (jump high) and JL (jump low). The instruction STI, for example, indicates that the next byte in rom 74 will be stored to the address that was given in the instruction. Another type of instruction is exemplified by STA (store A) which states that whatever is in the A register 152 should be stored to the address on the address bus. Therefore, the A register, rather than the rom, is enabled onto the data bus.

When the data selector 92 is addressed, it serves to latch certain test features which are addressed and defined above, i.e., DX, EOT, RDP, WRE, CL, WP and FCP. If the addressed test is true, an indication will be produced on test lead 66. The data selector is addressed via address bus 62 in conjunction with a jump instruction from decoder 80, whereby the aforesaid indication on test lead 66 will cause the program counter to jump to the next rom word. This next rom word prescribing a count in the program counter will now select a portion of the program.

Alternatively, the address reaching bus 62 via bus 86 may address the address decoder 88 or scratch pad memory 154 rather than data selector 92. As hereinbefore mentioned, address decoder 88 decodes selected addresses as indicated for operating certain of the peripheral devices illustrated in FIG. 3. The program defining the order of operations performed by the cassette subsystem is hereinafter described.

In the case of job search, the cassette subsystem causes a tape transport 122, 124 or 126 selected by register 112 to be read at 40 inches per second under the control of register 114. The selected tape is read and data selector 92 is addressed from the rom to indicate whether FCP (flux changes present) is indicated by detector 148. If flux changes are present, timer 116 is repeatedly reset to 175 milliseconds or the time spacing between jobs for a tape running at the given speed. If flux changes are not present, the data selector causes the program counter to jump to an instruction addressing the data selector to test for DX (delay expired). If the delay expires, i.e. timer 116 times out for 175 milliseconds with no flux changes, then program counter jumps the rom to provide a store immediate construction to the motion control register 114 for stopping the tape. Also, the status, i.e. end of job, will be stored in the scratch pad (see FIG. 35) for reporting to the status register in the interface (see FIG. 30). As hereinafter mentioned, the particular number designation of the job will be kept track of in the main memory 12 in FIG. 1, where such number is being incremented or decremented appropriately as each end of job status is reached. If the requested job number has not yet been reached, the central processor will supply another job search command to the cassette subsystem via interface 36.

In the instance of take search, the cassette subsystem recognizes a block of information as an end of take block. It will be observed that each block or PRU (physical recording unit) may contain an end of take byte or word substantially at the beginning thereof. As can be seen from procedure block 428 in FIG. 31, the end of take word, if present, is stored to register R4 in the scratch pad memory. Then, at the end of that particular PRU of information, the decision block 522 in FIG. 32 is reached for ascertaining whether the word in R4 indicates the PRU is an end of take, or a normal record. The compare gates 81 in FIG. 2 are utilized to compare the word for a normal record in rom 74 with the contents of R4 in the scratch pad memory. A jump instruction causes data selector 92 to initiate a jump if a comparison does not take place, thus indicating a take word was present. The program counter jumps to a count directing rom 74 to initiate a routine for stopping the tape deck and posting status. If the central processor unit determines the next take is not the numbered take desired, then a take search will be commanded again. Otherwise, readout will be commanded from the cassette subsystem into the main memory 12 in FIG. 1.

For executing a code search, the information from the selected tape is read a block at a time, such block consisting of 128 bytes or words, from the tape into the interface 36 from which it is read into memory 12 and specifically into the scroll memory portion thereof. The starting address in memory 12 to which information is to be read is obtained from the central processor unit, and each time a byte is stored to the main memory, the main memory address which is locally kept track of in the scratch pad memory is incremented such that each ensuing byte can be properly addressed in main memory. The central processor unit continues to make comparisons with the information in the target buffer as hereinbefore described, and the command to discontinue reading the tape will be given when a comparison is found.

Programming

In order to more fully understand the operation of this invention, it is helpful to understand the theory and organization of the system software.

The intelligent CRT terminal herein described is not a problem solving device, but rather a system for manipulating and editing manuscript data. The operator of the terminal does not program the device for problem solving but rather commands various functions by keyboard instructions to the CPU. The CPU processes the keystrokes according to programmed logic, frequently making decisions based on the contents of system status registers or tables of pre-stored data.

Each keystroke by the operator results in a response or chain of responses which are part of the editing or manipulating function. After the response or chain of responses occurs, the system returns to examine the operator's further keystroke instructions which direct the next step of the process. For convenience the preferred system includes a keystroke buffer in the main memory so that the operator may enter keystrokes at a rate of speed greater than the CPU can process commands. From the keyboard the operator controls the various peripheral devices and is able to accomplish such functions as inserting and deleting characters and words, transferring, deleting, storing and searching for blocks of text and searching for certain strings of character codes.

With plural mag tape storage units incorporated into the intelligent CRT editing terminal, the flexibility and capacity of the entire system is greatly enhanced. The memory capacity of the system is expanded without adding to the hardware memory capacity. The existing hardware memory is used more efficiently as a stage for locating and merging blocks of data as desired. The system provides for tape copying and is capable of translating input signals from a variety of devices into a code which may be visually displayed as screen characters. Likewise, the system can translate screen character codes into signals which may write a variety of output devices, including magnetic tapes.

The operator, provided with complete control of tape operations, can rapidly position, search, read, and write the mag tape units. Additional flexibility is achieved by programming the CRT terminal to perform automatically sequences of tape operations in response to commands from the operator.

In the preferred embodiment, this invention greatly increases operator access to stored text material by allowing him to search mag tapes in three ways. An automatic search may be made to locate the address of a text block on the tape. If the operator does not know the address of the text block he desires, the system will automatically search the text for a sequence of operator desired characters that appear in the text, or a visual search may be performed by the operator as the contents of the mag tape are written onto the CRT screen.

The ultimate purpose of the terminal which incorporates the various features described, is to provide an efficient interface between the operator and an automated photo-typesetter. Operator commands, read by the terminal, direct the processing of text material and at some point in time command the terminal to produce either a perforated paper tape, a mag tape, or a direct transmission of electrical signals which is used as input for a photo-typesetter. As major brands of photo-typesetters require different input formats a variety of separate editing terminal software products are required to adapt editing terminals for use with different photo-typesetters. To provide the desired degree of flexibility it is preferred that the software control system be composed of a series of tables which are hierarchically structured. These tables may be conveniently re-programmed to provide compatible input data for various photo-typesetters and to adjust terminal processing to accommodate other special needs of the user. Software elements subject to great change are coded in special macros to further simplify re-programming.

A. Command Processing

FIG. 4 is a flow diagram which shows the basic steps of the command processor. In the preferred system all commands are processed by a single command processor. A source obtains information from a peripheral device, e.g. keyboard, track ball, or a memory area, e.g. screen, multi-code and converts it into common command format. The command executive interprets the command format to locate and call the appropriate action procedure.

The finite state manager (FSM) serves as the command executive and is the primary system controller. The FSM gives a predictable response to any given command format "stimulus." In a single state system, this would mean that each stimulus S.sub.i produces a single predictable response R.sub.i from the FSM. For convenience in programming and economy of memory space, however, it is preferred that system software include several states. At any point in time the system exists in one of the identifiable states. The address of the current state is stored in a FSM register available for that purpose in the main memory. In the multi-state system the FSM determines not only which action procedure will be called, but also determines whether the present state will be maintained or whether the system will shift to a different state. Thus in a multi-state system, response R.sub.j, i, is defined for the stimulus S.sub.i when the stimulus is received while the system exists in state j. In the multi-state system, the response is not only an action procedure, but also may include a change in the system state by placing a new state address into the FSM register reserved for the current state status. In the preferred system, the stimuli are four byte words called operand quads, which are organized into a table. This operand table contains quads which link to every action procedure and state change required by the system. Sources translate external events such as a keystroke or character read from an input device into a location within the operand table. The quad at this table location is made available to the FSM which triggers the desired responses.

FIG. 5 illustrates the operation of the FSM in a multi-state system. Quad 8 is the stimulus read by the finite state manager. The FSM examines the FSM register in main memory and determines that the system is currently in state 2. Thus the stimulus quad is mapped to the quad 8 position in the state 2 table. The state table contains information which determines the action procedure and/or state change to be performed.

FIG. 6 illustrates the same process in a flow diagram. The FSM first calls the active source to transmit an operand quad if any is available. From the information in the quad, the FSM locates the address of a corresponding entry in the current state table. The state table entry, called a class action pair, is used to locate the address of an action procedure and of a state change procedure. The action procedure is called, and if a state change is required the change state routine is called.

When the system is at rest it is in the basic "keyboard" state and the keyboard source is active. In this system status the operator gives keystroke commands which control every feature of the system. A simple keystroke command given while the system is in the basic state will result in the triggering of a single action procedure and state change if appropriate. Other special keyboard states are provided for the formation of more complex commands. Some of these commands specify new sources which are to transmit stimuli for FSM processing and call routines which trigger a series of action procedures. Others allow the transfer of a keystroke sequences or character code strings into and out of memory locations. At the end of each sequence of command processing, the system returns to the basic state to check for further keystroke commands as given by the operator. Other states in which the system may exist during command processing include: input states, where data is read by a non-keyboard peripheral input device, processed and transferred to the scroll memory buffer; and output states, where data in the scroll memory buffer is processed and transferred to peripheral devices for output.

The key to a complete understanding of the hierarchical software control system is familiarity with the various tables and dynamic registers used in this system. These software devices located in the main memory of the system are basically used in three ways: 1. translation of input codes into operand table addresses and of operand table addresses into output code (I/O tables); 2. conversion of operand table addresses into operand quads which are the initial stimuli for command processing (operand table); 3. mapping by the FSM from the operand quad to the appropriate action procedures and state changes (class, state, procedure address and state address tables; dynamic registers).

1. PRIMARY TABLES

a. Operand Table

The operand table contains a four byte entry called an operand quad, for each function of the system. The operand quad is the initial stimulus processed by the FSM. There are four different types of quad in the preferred system. Each of these types serves a different purpose, and each has a different data format. All four types appear in one operand table. Every quad contains a class index position byte which the FSM uses to map to an action procedure and state change. The four quad types of the preferred system include:

Character quad. Each character quad contains coded information showing the character shift status (unshift, shift or super shift) and a class index position byte. A character quad may be provided by any source under appropriate conditions.

Multicode Quad. The multicode quad contains an address of the beginning of a multistring and a class index position byte. The keyboard source provides a multicode quad whenever the operator strikes a "character string" key on the keyboard. When the FSM processes a multicode quad, a string of character codes is transferred from a special location in the main memory to the scroll memory buffer. The CRT hardware causes the characters to be displayed on the screen. Character strings may be operator programmed or preset.

Action Quad. The action quad contains an address of a subroutine to be executed and a class index position byte which the FSM uses to find a link with the specified subroutine. The keyboard source produces an action quad when the operator strikes one of the "action" keys.

Function Memory Quad. This quad contains an address of a function memory string and a class index position byte. The keyboard source provides a function memory quad when the operator strikes a "function memory" key. The FSM maps from the quad to an action procedure which causes the string of key numbers stored in a function memory location in main memory to be processed as if they had been entered by operator keystrokes.

b. Class Index Tables

Class index tables are a software refinement incorporated in the preferred embodiment of the present invention to reduce the number of entries needed in each state table. A reduction is accomplished because the FSM can use a class index table entry to map from an operand quad to addresses in several different state tables. The current state status of the system determines which class index table is used for mapping and which state table is the object of class mapping.

c. State Tables

A state table can be defined for each possible system state. The table contains a pointer to the class index table which is proper for mapping to that particular state. Following the pointer is a list of one or more two-byte entries called "class action pairs." Each class action pair contains a "procedure command byte" which points to a position in the procedure address table and "state command byte" which points to a position in a state address table.

d. Procedure Address Table

The procedure address table contains an address for every action procedure. Class action pairs from each state table contain "procedure command bytes" which point to locations in this table.

e. State Address Table

The state address table provides an address for every possible change of state. The table determines what state the system will be in at the end of each cycle of FSM processing. State changes may be either absolute or relative. If the "state command byte" pointer of a class action pair contains a positive value, the state change is absolute. The new system state is defined by the state address to which the state command byte points in the state address table. If the state command byte contains a negative value, the state change is relative. A relative state change causes the system to return to the immediately previous state. If the state command byte contains a value of zero, there is no state transition.

A flow diagram for the state change process appears in FIG. 7. In this figure when the state change routine is called, i.e. if the state command byte is not equal to zero, the state change routine may follow two paths. If the state command byte is positive an absolute state change occurs. The old state address is added to the state stack and the new state address shown in the state address table is entered in the appropriate FSM register as the "current state address." If the state command byte is negative the state change is relative and the last previous entry in the state stack is entered as the "current state address."

2. Control Tables

The following control tables provide for state transition control and a means of preserving the status of a state group:

a. State Stacks

The state stacks are single pointer, last in-first out circular stacks. In the preferred system these stacks have sufficient capacity for eight one byte state entries. An absolute state transition causes the state stored in the FSM "current state status" register to be pushed onto the top of the stack. A relative state transition causes the last prior state to be popped from the stack and placed in the FSM register.

Three separate state stacks are maintained by the system, one for each primary mode of the preferred system (keyboard, input and output). This provides a means of preserving the state status of each mode. Each of the system states is classified into one of the primary modes according to source. All of the states for which keyboard or multicode is the active source are included in the keyboard mode; those states for which screen is the active source are included in the output mode; and those states for which input is the active source are included in the input mode. According to the programming rules of the preferred system, state transition between states in different modes is not allowed during FSM processing. Transition between modes is by means of a special routine, which is called during input/output processing.

b. State Status Tables

In addition to the three state stacks certain dynamic information must be saved for each mode. The current state address, the current class index address, the state stack pointer, the base of the state stack and the address of the current (active) source are held in state status areas of the main memory.

3. Dynamic Registers (FSM)

The following registers contain dynamic information used during FSM processing:

a. Special Control Area

This register contains the state command byte used for control of the state machinery, and the procedure command byte (jump instruction), used for executing action quads.

b. Operand Quad Storage Area

This register contains the first three bytes from the operand quad, a pointer to the quad in the operand table and a class index position byte. The format of quads varies depending on the type of quad stored.

c. State Status Area

This register contains the current state address, the current class index address, the stack pointer, current stack base and pointer to the current stack of the active primary mode.

The use of the primary tables is shown in FIG. 8. The tables demonstrated in this example of FSM processing include: an operand table which contains eight, four-byte operand quad entries; two class index tables for mapping to the various states; three state tables each containing a pointer to the appropriate class index table and four two-byte class action pairs; a procedure address table containing five precedures addresses; and a state address table containing three state addresses. At the beginning of this example, the current state address is state 2. It can be seen from the class index address pointer in state table S2 that state 2 uses class index tabel C2 for class mapping. States 1 and 3 use class index table C1 for class mapping. FSM processing begins when the active source selects a quad from the operand table, in this case quad 7. For quad 7, the class index position byte, the fourth byte of each operand quad, is 3. The FSM responds to this class index position byte by examining the third position of class index table C2. The 4 found in this position is a pointer to the class action pair in the fourth position of state table S2. This class action pair points to positions in the procedure address and state address tables. The 2 in the first (procedure command) byte of the class action pair shows that the second position of the procedure address table contains the address of the action procedure to be performed. In this example, the second position of the procedure address table contains the procedure address of action procedure 1. The second (state command) byte of the class action pair contains a positive value and thus calls for an absolute state change. The new state address, S3, is found at position 3 of the state address table. After the action procedure is complete and the state change has been made, the FSM calls upon the active source to provide for processing a new quad.

FIG. 9 illustrates two state transition cycles. The diagram shows the contents of the current state stack and relevant FSM registers both before and after each state change. In the first column a segment of the state table S2, the state stack of the mode which includes state 2, and FSM registers containing state address, class address, and the stack pointer are shown. A history of prior state activity is shown by the state addresses recorded in the stack. In this example states 5, 2, 1 and 3 were previously active in that order, 5 being the most recent prior state. The stack and state address register (STADD) show that state 2 is now the active state. That class 3 is the appropriate class indexing into state 2 is shown by the class index address pointer in state table S2. The class address, C3, is also stored in the class address register (CLADD). The stack pointer shows position 5 to contain the most recent entry in the state stack.

The first state transition cycle illustrates the same absolute state transition shown in FIG. 8. Column I shows the contents of the state stack and FSM registers before the transition. In this cycle, the class action pair located at position 4 of state table S2 has been selected. The positive value, 3, of the state command byte of this class action pair indicates that the state address in the third position of the state address table, shown in FIG. 8, indicates the next active state. Also, in accord with FIG. 8, the state address in the third position of the state address table is S3. The transition is made by advancing the stack pointer one position to position 6. The new state address, S3, is then entered into the stack and STADD. The system status after this absolute state transition is shown in column II.

The second state transition cycle illustrates a relative state transition. Column II shows the system status before this transition. At the beginning of this state cycle the FSM received a quad which mapped to the third position in the current state table, S3. Because -1, the value of the chosen state command byte, is negative, the stack pointer does not advance to stack position 7, but rather moves back one position to position 5. S2, the state recorded in state stack position 5, becomes the new active state. STADD and CLADD are updated accordingly. The system status after this relative state transition is shown in column III.

4. Sources

Sources translate input stimuli into a form suitable for FSM processing. Each source uses some combination of input/output table mapping to locate a quad in the operand table and to move the contents of that quad into the FSM register. The four sources incorporated in the preferred embodiment of the present invention are described below:

a. Keyboard Source

Each keystroke by the operator causes the keyboard source directly to locate an appropriate quad in the operand table and to store the quad in the FSM register. In the preferred system, a buffer is provided to receive keystroke stimuli so that the operator need not wait after each keystroke until processing of that stimuli is complete before entering subsequent keystrokes. The keyboard handler is a subroutine called by the keyboard source to retrieve key numbers from the keystroke buffer. The keyboard source translates these stimuli into an operand table address.

FIG. 10 illustrates the operation of the keyboard source in a flow diagram. The keyboard handler, shown in this figure as a part of the keyboard source, appears inside the broken lines. When keyboard is the active source, the FSM calls on keyboard source to provide a quad for processing. The keyboard source in turn calls the keyboard handler to check continuously the keystroke buffer for stored key numbers. If this buffer is empty the system continues in loop checking again and again until keystroke data is entered. If the buffer contains data, the keyboard handler takes the first key number entered in the buffer and advances the buffer pointer to the next position. The keyboard handler gives this key number to the keyboard source which uses it to locate a quad in the operand table. After the quad is stored in the FSM register and the FSM has mapped from the quad to appropriate action procedures and state changes, the keyboard source is inactive until called by the FSM to provide another operand quad.

b. Input Source

Operation of the input source is shown in FIG. 11. The input source is active only when the system is in the input mode. When the FSM calls upon the input source to provide a character quad, the source calls the input handler, FIG. 16, to obtain an octal code from either a mag tape unit or the paper tape reader. The input handler sends this code to the input source which maps through the input table to the address of an operand quad. The input source loads the quad into the FSM register for further processing, then exits until it is called again by the FSM.

c. Multicode Source

The multicode source is illustrated in FIG. 12. Multicodes are strings of screen character codes stored in a special area of the main memory designated the multicode table. The operator retrieves a multicode string by striking a key which corresponds to the desired string. The keyboard source uses the keystroke to locate a multicode quad. The FSM maps from the quad to an action procedure which changes the active source from keyboard to multicode. On the next cycle of FSM processing, the multicode source is called to provide a quad. Memory pointers are advanced to first position of the designated multicode string. The multicode source takes the screen code symbol from the position indicated by the memory pointer. This character is examined to determine whether it is the special character which signals the termination of the multicode string. If it is such a special character, keyboard is restored as the source. If the character at this position is not the special termination character, the multicode source converts it by means of input and output tables to an operand table position. The character quad located at that position is moved into the FSM register. FSM processing maps to an action procedure which causes the character to appear on the screen. When this action procedure is complete, the FSM calls multicode, which is still the active source, to provide another quad. The multicode source routine is thus repeated until the termination character is encountered.

d. Screen Source

Operation of the screen source is diagrammatically illustrated in FIG. 13. The screen source provides character codes for output to the paper perforator and mag tape units. In the preferred system, screen is the only active source of the output mode. When the FSM calls the screen source to provide a character code, the screen source first checks to see whether it is at the end of a line on the screen. If so, keyboard is reset as the active source and the system returns to the keyboard mode. If however, it is not at the end of a line, the screen source obtains from the visual area of the scroll memory, a symbol for the next displayed character. This screen symbol is converted through input and output tables to a position in the operand table via the convert routine. Information from these tables is moved into the FSM register. The FSM uses this information to map to an action procedure which calls the output handler, FIG. 17, to write the code on the chosen peripheral output device. The screen source then advances the memory pointer to the position of the next screen code.

5. I/O Table Processing

The use of input and output tables is mentioned above in conjunction with certain source processing procedures. These short tables, located in the main memory, are used to translate between two character code structures which have different data formats. The use of two different character codes, commonplace in CRT editing systems, is a convenience which both maximizes editing flexibility and yet provides a space-saving output format compatible with most phototypesetters.

The primary difference in data formats is the coding of the character shift status. In the format used by the CRT logic (ASCII), the code symbol for each character contains information which both identifies the character and indicates the shift status of that character. The format used on paper and magnetic tapes (TTS) is composed of code symbols which contain either character or shift status information, but not both. In a string of TTS symbols each consecutive character code is treated as if it has the same shift status as the previous one. In order to indicate changes in shift status, it is necessary to insert shaft codes in the string. Because TTS codes contain less information, they take up less space on magnetic or paper tapes and are historically preferred by the typesetting industry. It is not, however, convenient to use TTS codes for editing functions. When TTS character codes are moved, deleted or added to a text string, it is frequently necessary to add, remove or change several TTS shift codes in order that all characters in the revised text string may have the desired shift status. Editing is much easier with the ACSII code because each character code possesses its own shift status information and may be moved into or out of any portion in the text string without affecting or being affected by other characters in the text string.

The input tables provide a convenient way to translate TTS codes read by paper and mag tape readers into ASCII format for ease in editing. After editing is complete, as a part of output processing to magnetic or paper tape, the character codes are translated from ASCII into TTS format via the output table.

B. Device Handlers

A preferred embodiment of the editing system provides interfaces for a variety of hardware input/output devices including a keyboard, track ball, paper tape reader, paper tape perforator, Phillips magnetic tape cassettes and CRT.

1. Device Registers

A portion of the main memory is reserved for software interfacing with the input/output hardware. Various locations in this memory area are assigned as device registers, and are addressed in the same manner as main memory. These hardware registers provide device control, status information and data buffering for communications between the CPU and the various peripheral devices.

2. Interrupt

In order to achieve maximum speed in processing, the present invention may include a hardware interrupt system which allows certain of the peripheral devices to function asynchronously with CPU processing. These devices function independently until they require the services of the CPU. At this point in time the routine being processed by the CPU is interrupted while the CPU services the interrupting peripheral. After servicing, the CPU continues with the interrupted routine.

Each peripheral can have a hardware pointer to one of the locations in low memory. At the time of an interrupt, the current value of the CPU program counter is pushed into an internal call stack and the program counter set to the selected interrupt vector location. After CPU servicing of the peripheral, the previously saved value is returned from the call stack, and the CPU program counter is set to this value.

The vector locations are typically used for short routines that both save the register environment and execute an "interrupt service routine" (ISR). An ISR provides for interrupt service processing and, thereafter, the restoration of the register environment. In a preferred embodiment of the present system, the paper tap punch, keyboard and track ball are interrupting peripheral devices.

3. Peripheral Devices

a. Keyboard

Keyboards are well known and may exist in a variety of configurations. For convenience in the editing functions of the preferred system, keyboards are organized into three separate key banks. The "main key bank" of approximately 80 keys contain all the characters and symbols of a typical alphanumeric keyboard. The "auxiliary key bank," containing about 40 keys is used for a variety of purposes, including control of the memory processing routines. The "system control key bank", providing about 25 keys, is the origin of all system control commands from the operator.

Each of the keys on the keyboard is assigned a "key number." When the operator strikes a key, the corresponding key number is transferred to a "keyboard data buffer register" in the device register area of the main memory. In response to this condition, the CPU interrupts processing and calls the keyboard ISR. This ISR transfers the key number from the keyboard data buffer register to a circular keystroke buffer in the main memory. The buffer is emptied by the keyboard source in the normal course of command processing. The keyboard ISR is sensitive to the "attention" key of the system control keyboard. This key causes a special panic flag to be set in a main memory register. The keyboard source reacts to this flag and causes the circular buffer to collapse.

The operation of the keyboard ISR is shown in FIG. 14. When an operator keystroke calls the keyboard ISR, if the attention key number is stored in keyboard data buffer register, a panic flag is set. If, however, any other key number is stored, the keystroke buffer pointer is advanced one position and that key number is stored in the keystroke buffer. Information stored in the keystroke buffer is processed by the keyboard source as previously described.

The effect of the panic flag on keyboard source processing is shown in FIG. 15, an expanded view of the keyboard source. When the keyboard source is called by the FSM, it first examines the appropriate main memory register to determine whether a panic flag has been set. If the keyboard source discovers that the panic flag has been set, it will collapse the keystroke buffer, exit and await new entries in the keystroke buffer. If the panic flag has not been set, the keyboard source examines the buffer for a stored key number. If a key number is not found in the buffer, the routine returns to the beginning to look again for a panic flag, and in this fashion continues in a loop until either a key number or a panic flag is detected. If a key number is found in the buffer, it is processed in the fashion previously described.

b. Track Ball

The track ball interface translates and writes the direction of movement of the cue ball apparatus into a coded four bit value in the device data register in main memory. Bits 0 through 3 are set corresponding to left, right, up and down, respectively. Responding to the condition of this register, the CPU interrupts processing and calls the track ball ISR. ISR invokes the appropriate cursor movement routine consistent with the coded bit pattern.

The cursor is a symbol which appears as a shaded overlay on the screen of the CRT at all times. This symbol may be moved by the track ball control to any character position on the CRT screen. It is used an an indicator to show the point at which a given operation is to take place. For example, if a character is to be deleted from the screen the cursor is moved to a position over the character to be deleted. When the appropriate action key is struck to call the DELETE subroutine, the character under the cursor is removed, all the characters to the right of the cursor are shifted left one position and a null character is added in the last position in that line.

c. Paper Tape Reader

In the preferred editing system, the paper tape reader is not enabled as an interrupting device, i.e. it must wait until the FSM calls for data in the normal course of input source processing. When the input source, FIG. 11, calls the input handler, FIG. 16, to provide a character for processing and the operator had designated the paper tape reader for input, the paper tape input handler obtains a character from the paper tape reader and transmits it to the input source for further processing. The paper tape input handler controls both movement of the paper tape and detection of character codes.

d. Paper Tape Perforator

In the preferred editing system the paper tape perforator is enabled as an interrupting device and functions asynchronously with screen source processing. Interfacing between the paper tape perforator ISR and the output handler, FIG. 17, is by means of a circular buffer filled by the paper tape output handler and emptied asynchronously by the ISR. When the buffer is empty ISR service ceases until it is enabled again by the paper tape output handler.

e. Cathode Ray Tube

The preferred CRT display subsystem provides a visible display organized as a matrix of character positions in lines and columns. Optional features incorporated in the preferred embodiment include: direct addressing of the display positions, and one or more screen lines, called format lines, which are reserved for system status information.

f. Cassette Subsystem

This subsystem as hereinbefore described provides the ability to read and write strings of character physical records and to position magnetic tapes according to job and take designations chosen by the operator.

Registers associated with the cassette subsystem contain locations for a variety of coded information including the following: a bit to indicate interrupt is enabled, status codes, command codes, the address of the magnetic tape unit selected, and the address of the current position in the mag buffer of the main memory. The main system directs cassette subsystem activities by transmitting one of the following command codes to a command code register: rewind, take search, forward job search, reverse job search, read a block or physical recording unit (PRU), write a normal PRU, write an end of take PRU or write an end of job PRU. The CYCLE routine, FIG. 30, of the cassette subsystem reacts to these commands by calling a cassette subsystem subroutine which performs the commanded operation.

At the end of cassette subsystem processing, the STATUS cassette subsystem routine, FIG. 35, posts a subsystem status code which is transmitted to the main system via a status code register. This status code indicates the type of PRU most recently processed. Three types of PRU exist in the preferred system including: normal PRU, end of take PRU, end of job PRU.

File Organization. The organization of tape records into PRU's is one aspect of magnetic tape file organization. The other aspect is the logical format of the stored characters.

According to the "logical format" of the preferred embodiment, codes recorded on a magnetic tape are organized into units called jobs and takes. Each character string consists of one or more jobs. The end of a data string to be recorded on a magnetic tape is indicated by an end of file (EOF) code. Each job consists of one or more takes and is terminated by an end of job (EOJ) code. A take is a variable length character string that is terminated by an end of take (EOT) code. No size limits are imposed on the length of the jobs or takes other than the physical capacity of the magnetic tape. FIG. 18, showing a sequence of EOJ, EOT and EOF codes, is one example of logical tape format.

EOT and EOJ codes are set in the scroll memory character string in the same way that characters are set. In the preferred system, EOT and EOJ keys are provided in the system control keyboard so that the operator may set these termination codes as characters entered via the keyboard.

According to "physical format" rules, magnetic tape codes are organized in blocks called physical recording units (PRU's), FIG. 20. Each PRU in the preferred system contains an EOT or EOJ byte and a fixed number of data bytes (128 bytes in the preferred system). The EOT or EOJ bytes are set if the PRU serves as one or both of those terminators. In addition, EOJ PRU's are followed by a gap of blank tape. Longer tape gaps signal an EOF or "logical end."

Unlike the jobs and takes of logical format, the PRU's of physical format are all of a single fixed length.

In the preferred process of recording PRU's, character codes are added to the string until 128 bytes are filled or until an EOT or EOJ code is encountered. If one of the terminator codes is found, the record byte string is ended and a new PRU begun even if the original PRU has less than 128 character bytes filled with useful codes.

Whenever a magnetic tape unit is called upon to rewind, EOJ and EOF tape gaps are set if appropriate. FIG. 19 shows this rewind logic. Before a physical tape rewind occurs, this software routine determines whether the active magnetic tape unit was last enabled to receive output data. If it was, the software rewind routine, FIG. 19, commands the cassette subsystem to insert EOJ and EOF gaps after the character string. A physical rewind is then completed according to the REWIND subroutine, FIG. 33, of the cassette subsystem and the registers which contain tape status information are updated to reflect the current tape position. If the unit was not most recently enabled to receive output data, a rewind and update of tape status registers occurs without setting the EOJ and EOF gaps.

Mag Tape Handler. Those parts of the input and output handler routines which control magnetic tape operations from the central processor are called mag tape handlers. The mag tape input and output handlers provide the following services: mag buffer management, input source and screen source interfacing, and file positioning. Each of the cassette drive units is provided with dual character buffers (two 128 position buffers for each unit in the preferred system). The filling, emptying, switching, flushing and discarding of these mag buffers, consistent with source processing and file position requirements of the editing system, are controlled and managed by the mag tape handlers.

Software registers in main memory retain information concerning tape position and mag buffer status for each cassette unit. The register names and purposes are described below:

Mag.sub.n -- Tape of last PRU read or written on unit n;

Front.sub.n -- Character left in current active mag buffer for unit n;

Pntr.sub.n -- Pointer to next active character in current active mag buffer for unit n;

Jobtp.sub.n -- Job number of last end of job PRU read or written on unit n;

Tketp.sub.n -- Take number of last take PRU read or written on unit n.

n = magnetic tape unit number.

FRONT and PNTR are used primarily for source interface processing. The character-by-character mag buffer processing and decisions to switch mag buffers and activate additional I/O character transfers are controlled by the status of these registers. JOBTP and TKETP are used in the tape position logic for job/take search processing. MAG provides information on the type of PRU most recently processed. The information in MAG is used for updating job and take registers and for detecting the logical end of tape (EOF). This information, as to status of active I/O units, is displayed to the operator on the format line of the CRT screen.

FIG. 16 is a flow diagram illustrating the operation of the mag tape input handler. When the FSM requests data from the input source, FIG. 11, that source calls the input handler, FIG. 16, to obtain a character. The input handler examines the input flag, registers set by prior operator keystrokes, to determine which unit has been flagged for input. If one of the mag units is flagged, mag tape input processing is invoked as shown in FIG. 16. The mag tape input handler first checks to see whether the active mag buffer of the selected unit is empty. If it is not, the next character is retrieved from this buffer and sent to "input" block of input source, FIG. 11. If the active mag buffer is found to be empty, the mag tape input handler checks to see if the end of the tape has been reached. If it has, processing is terminated and the system returns to be keyboard mode. If it is not at the end of tape, the mag tape input handler commands the cassette subsystem to fill the just emptied buffer with characters of the next PRU on the mag tape. While that is being done, the other buffer, which was previously filled in the same way, is then made active and its first character selected for input source processing. CPU control is then returned to input source, FIG. 11.

FIG. 17 illustrates the mag tape output handler and shows the operation of the dual buffer system. When the FSM receives a character from the screen source, it calls the output handler to write the character on an output device. The output handler, FIG. 17, examines the registers of the output flag word to determine which output unit was flagged by the operator as active. If one of the mag units is flagged, mag tape output processing is invoked as shown in FIG. 17. The mag tape output handler stores characters in mag buffers and then transfers them to the tape if there is space available. First the mag tape output handler stores the character in the active buffer of the designated mag unit. Then, if this mag buffer is full, the handler switches to the second mag buffer assigned to the same unit. If the active mag buffer is not full, the mag tape output handler checks to see if it has just switched to a new mag buffer, i.e., if the pointer is at the first position of the active mag buffer. If the pointer is at the first position, the mag tape output handler examines the other buffer of the same unit. If the other mag buffer is not full, or if the active buffer pointer is not in the first character position, the mag tape output handler updates the mag buffer pointers and then exits. If, however, it is in the first position of a mag buffer and the other mag buffer is full, the mag tape output handler commands the cassette subsystem to write the contents of the other mag buffer onto the tape. After the contents of a mag buffer are written on the tape, a check is made to determine whether the end of tape indicator passed the tape heads during the write operation. If it did, the operator is so notified. If it did not, the routine terminates until called again by the FSM.

4. Examples

The following examples describe typical operations of the various preferred device handlers.

a. Keyboard to Screen

This example illustrates transmission of a character symbol from the keyboard to the screen when the following conditions exist:

1. Keyboard state is active (keyboard mode);

2. Keyboard is source;

3. Cursor is positioned at upper left corner of screen.

When the operator strikes a character key, command processing is interrupted. The keyboard ISR, FIG. 14, transfers the key number to the keystroke buffer. Later, when the FSM, FIG. 6, calls the active source to provide a quad, keyboard source, FIG. 10, removes the key number from the keystroke buffer, maps to an operand quad, and loads the quad into the FSM register. The FSM, FIG. 6, examines the quad, reacts to the class index position byte, locates and calls the procedure SCREEN. The SCREEN procedure examines the shift word, a register which contains operator instructions as to shift status, retrieves the appropriate screen code from the stored operand quad, and gives the screen code to the CRT subsystem for display on the screen.

b. Paper Tape to Screen

This example describes transmission of character information from the paper tape reader to the screen when the following conditions exist:

1. Input state is active (input mode);

2. Input is source;

3. Reader is positioned for next character;

4. Cursor is positioned for the next vacant screen position.

This operation is commenced when the FSM, FIG. 6, calls upon the current source, input source, to provide an operand quad. Input source, FIG. 11, calls the input handler, FIG. 16, to provide a character code. The input handler examines the input flag word and, determining the paper tape reader to be the selected input device, calls upon the paper tape input handler, also FIG. 16, to read a character code from the paper tape. The input handler transfers this code to the input source which maps through the input table to locate an operand quad. The input source then stores the quad in the FSM register. The FSM examines the quad, reacts to the class index position byte and selects the procedure INCHR. INCHR calls the procedure SCREEN. SCREEN examines the shift word, selects the appropriate screen character code and sends it to the CRT subsystem for display.

c. Magnetic Tape to Screen

This example describes transfer of a character code from a magnetic tape to the screen when the following conditions exist:

1. Input state is active (input mode);

2. Input is source;

3. Cursor is positioned correctly;

4. Mag buffer is partially full.

When the FSM, FIG. 6, calls the current active source to provide an operand quad, input source, FIG. 11, calls the input handler, FIG. 16, for a character code. Input handler examines the input flag word and determines that a magnetic tape unit has been specified as the origin of input. The input handler thus calls upon the magnetic tape input handler, also FIG. 16, to retrieve an input code from the appropriate mag buffer and to adjust the buffer pointers. Input source maps the magnetic tape character code, via the input table, to a position in the operand table. Input source then transfers the located quad to the FSM register. The FSM examines the quad, reacts to the class index position byte and selects the procedure INCHR. INCHR calls the procedure SCREEN. SCREEN retrieves the screen character from the FSM register. The screen character, consistent with the shift word, is then sent to the CRT subsystem for display on the screen.

d. Screen to Output Device

This example illustrates transfer of a character displayed on the screen to a peripheral output device when the following conditions exist:

1. Output state is active (output mode);

2. Screen is source;

3. The cursor is positioned over the correct screen code.

When the FSM, FIG. 6, calls upon the active source to produce an operand quad, screen source retrieves the screen character under the cursor. Screen source maps via the input and output tables, from the character code to a position in the operand table, transfers the located quad to a FSM register and advances the cursor one position. The FSM examines the quad, reacts to the class index position byte, and selects the action procedure PUT. PUT retrieves the output code from the FSM register and stores it in the output buffer. The output handler, FIG. 17, determines from the output flag word which device is enabled for output, then calls either the paper tape or magnetic tape output handlers, FIG. 17. The chosen handler retrieves the output code and writes the appropriate peripheral device.

C. CRT Screen Manager

The CRT screen manager includes the routines which cntrol standard editing functions of CRT editing terminals. The CRT manager of the present invention incorporates such features as block management, multicode processing, and a procedure for searching the screen memory to locate operator-selected strings of characters.

1. Scroll Memory

As previously described, the preferred system contains a hardware memory area for the storage of character codes. Because of limited CRT screen capacity, only a portion of this memory area may be displayed at a given time. For ease in locating and manipulating data, the memory is organized as a scroll. The entire memory area contains a "belt" of data which can be scrolled up or down at will. The CRT display is a "window" through which to view a portion of the belt. The display allows the operator to view what is stored in a chosen area of the memory and to observe changes as they are made.

The scroll feature provides a means of exchanging text material between the undisplayed storage area of the scroll memory and the visible storage area. The undisplayed storage area is divided into upper and lower parts. In a "scroll down" operation a line is moved from the bottom of the screen and placed in the bottom part of the undisplayed memory. The remaining lines on the screen are each moved down one line. A new line is then taken from the top part of the undisplayed memory and displayed as the first line on the screen. A "scroll up" operation reverses this procedure.

A word wrap feature may be incorporated to insure that words will not wrap from one line to the next. If a word will not fit at the end of a screen line, the entire word is placed at the beginning of the next line. A word fragment at the end of the bottom screen line is returned to lower memory. The word wrap feature also provides paragraph ending capability. A special screen symbol may be assigned to serve as a line terminator. Text transmission from lower memory stops when this symbol is encountered and any remaining character positions on that line are filled with nulls.

A special refit operation is provided in the preferred system to clean up the screen after editing operations, such as input and delete, have altered the configuration of characters on the screen. Text material is flushed from the screen into lower memory and then scrolled back onto the screen consistent with word wrap and line terminator rules.

2. Multicode Processor

The preferred editing system reduces the number of keystrokes necessary for text preparation and editing by means of multicode keys. When the operator strikes one of these keys, a pre-recorded string of one or more characters is inserted into the text string on the screen. Multicode keys may be preset with character strings or for greater flexibility may be linked to character string memory areas which are loaded by the operator.

In the preferred system two keys are provided for changing the contents of character string memory areas: "load memory" and "end load memory." To load initially or later change the contents of a character string memory area, the load memory key and one of the numbered multicode keys are struck. This causes the screen display to change. The contents of one screen line are temporarily displaced by a line containing the contents of the chosen character string memory area. The operator may now add, change or delete characters on this line. When editing is finished, an end load memory key is depressed, terminating the modification session. The modified string is stored in the character string memory area at the proper location within the memory table and the screen is returned to its previous status.

In the preferred system, memory tables are provided for use by the multicode processor to store the character strings. Characters are most conveniently stored in screen format (ASCII). Strings in the memory tables are separated internally by octal codes.

When a multicode key is struck by the operator, the keyboard source maps this stimuli to a multicode quad in the operand table. The first two bytes of the quad contain a pointer to a character string memory area in the appropriate memory table. The quad is processed by the FSM which calls action procedure MACC to switch the source from keyboard to multicode source. The MACC also provides the multicode source with the string pointer. As previously discussed, the multicode source maps character codes into the operand table one at a time, in response to calls of the FSM. The quads are processed and the characters are displayed on the screen. When the string is exhausted the multicode source provides a quad to the FSM which results in restoration of keyboard source.

3. Block Management

A block management or "move" function is a feature commonly incorporated in editing systems which possess a CRT scroll memory.

The CRT screen manager of the present invention provides such a means of manipulating blocks of text material within the boundaries of the scroll memory. Blocks may be transferred from one point of the text string to another, stored, restored or deleted. In the preferred system, a block is first bounded by special screen characters which appear as octal codes in the text string and as block boundary characters on the screen. The operator sets a block boundary character by moving the cursor to the desired location in the text as it appears on the screen and striking the "block define" key on the system control keyboard. After the beginning and the end of the block are defined, the operator commands the type of action to be taken. In the preferred system the type of action is determined by the location of the cursor at the time the operator strikes the "block transfer" key on the system control keyboard. When the block transfer key is struck, a defined block is "saved" if the cursor is located on one of the block boundary positions, a previously saved block restored to the cursor position if no current block has been defined, and a defined block transferred to the cursor location if the cursor is not located on a block boundary position. The system will also delete a defined block upon appropriate commands from the keyboard.

A typical operation begins by moving the block management text area into bottom memory. This includes the defined block and/or the transfer point. FIG. 21 shows a text string in the bottom memory as it would exist just prior to a typical block transfer operation. The text is the lower memory is divided into four strings by octal codes inserted when the operator struck the block define and block transfer keys. In this example, string 2, the defined block, is shown bounded by a bracket. Strings 3 and 4 are divided by the transfer point. String 1 is a string fragment from the screen and is not a part of the transfer operation.

After the boundaries and transfer point have been set and the block management text area moved to bottom memory, the scroll memory moves text strings from the bottom memory to the screen. In this example, strings 1, 3, 2 and 4 are moved to the screen in that sequence.

4. Code Search

An important feature of the present invention is the code search routine which is a part of the CRT manager. This routine provides the means of searching the screen scroll memory, and input text for a key word or phrase. In the preferred system the operator defines the search argument by striking the "define search" key on the system control keyboard. This causes a line on the screen to be blanked. The operator then loads the search argument in the same fashion multicode keys are loaded. The search define key is struck a second time to fix the search argument and return the screen display to normal configuration. After defining a string of characters as the search argument, the operator may command the type and extent of the search operation by keystroke commands. When found, search action is terminated and the cursor positioned on the first character of the located character string.

According to the logic of the preferred code search procedure, a text block is searched to find any contiguous or non-contiguous string of character codes which matches the search argument. Only after such a string is located is it tested for contiguity. A contiguous string in the text which is found to match the search argument satisfies the search.

FIG. 22 illustrates successful and unsuccessful code searches. The left hand column of FIG. 22 shows a search argument. String 1 is a typical string of characters to be searched. Position numbers which appear at the left of the text strings in this figure are added for ease of explanation. The search begins by selecting the first character of the search argument, in this case the letter A. The text is searched and the letter A is located at position 2. The letter B from the search argument is then selected, searched for and found at position 5. The search continues until the D is found at position 11. At this point the search is reversed and an attempt is made to match the search argument against the characters in positions 11, 10, 9 and 8. In the example of string 1 the search has failed. String 2 of FIG. 22 shows an example of a successful search. During the forward search the letter A is found at position 2, B at 4, C at 6, and D at 11. The letters A, B and C at positions 8, 9 and 10 were not seen during the forward search. When reverse search was made for contiguity, however, the characters located in positions 11, 10, 9 and 8 were found to match the search argument. Thus, the search of string 2 was successful.

The software logic of the code search operation appears in FIG. 23. At the time this routine is called, the operator has already set the search argument and defined the text string which is the object of the search. The search argument is stored in an area of main memory called the search target buffer. A text string which is the object of the search is located in the visible area of the scroll memory. In the preferred system the actual searching is performed on the "screen" and the search routine operates independently of the manner in which text material is placed on the screen. Thus, if the search argument is not found on the screen, the search can be extended either by scrolling material onto the screen from the bottom memory or by inputting material onto the screen from an input device, and, in particular, from a mag tape device.

When the routine of FIG. 23 is called, it goes to the start of the text string on the CRT screen which is the object of the search. It then retrieves the first search argument character from the search target buffer and proceeds through the text string on the screen comparing each character of the text string with the first character of the search argument. This comparison operation is shown as loop 1 in FIG. 23. If the search continues to the end of the bottom line of the screen without finding a match with the argument character, the routine returns control to a sequencer called the screen executive, FIG. 27. The code search routine remains inactive unless the screen executive scrolls up the screen, calls for new data on the bottom line and recalls the code search routine.

If the first character of the search argument is matched in the displayed text string, the code search routine obtains the next character in the search argument from the search target buffer. If the character obtained is not the terminator code of the search argument, the code search routine returns via loop 2 and continues to compare the new search argument character with characters in the text string. This process continues until finally either the search argument has been entirely matched or the text string has come to an end without a complete match. If the routine detects that it is at the end of the argument string, i.e., all of the argument characters have been matched, a reverse search of the text string is made beginning with the last character matched. If during this reverse search each character of the text string matches the corresponding character of the search argument, contiguity has been established, the cursor is displayed at the start of the phrase on the screen which matches the search argument and the code search routine returns control to the screen executive. If, however, a backward search finds no contiguity, the code search routine returns, via loop 3, to begin the searching process again. The renewed search begins by comparing the first search argument character with the text string character last examined in the previous backward search for contiguity. The forward searches for matching text characters and reverse searches for contiguity will continue until finally either a match is found or the text string is exhausted.

Because of the convenience of the code search routine, as well as the other search routines, the cassette subsystem incorporated into the main system provides an editing terminal with an almost limitless data capacity. While an operator can visually scan the contents of the scroll memory to find a desired search argument, it is a great inconvenience for the operator to search cassette files in this manner. The automated code search routine greatly enhances the efficienty of the CRT editing terminal with magnetic tape units.

In a code search of data from a magnetic tape, input source, FIG. 11, is the active source. Each time the screen executive seeks new data to fill the bottom screen line, it calls on FSM, FIG. 6, which in turn calls upon input source to provide a character. Input source calls mag tape input handler, FIG. 16, which obtains a character from the appropriate mag buffer. FSM continues to call for character quads until the bottom screen line is filled. When the line is filled, the screen executive calls the code search routine, FIG. 23. If, during processing, the mag buffer is emptied, the mag tape input handler sends a "read a PRU" command to the cassette subsystem. The CYCLE routine, FIG. 30, responds to this command by calling the READ WRITE subroutine, FIG. 31. This subroutine causes a PRU to be read into the mag buffer and then calls the STATUS subroutine, FIG. 35, which informs the main system of the type of PRU read.

D. Input/Output Controller

For speed and convenience the preferred editing system is programmed to perform selected sequences of input/output functions on a continuous basis without operator intervention. All throughputting operations are suitably terminated on encountering an end of job from the active cassette designated for input. The input/output controller includes all of the software that directs such throughputting activities. A command language, dislcosed below, is utilized by which the operator programs the controller and designates which input and output units are to be used. A routine called the screen executive, FIG. 27, is provided which, when called by the operator, will perform a series of input/output operations, continuing until an entire throughputting operation is complete or interrupted by a keystroke command from the operator. In addition, file protection features may be incorporated in the input/output controller to protect against the unwanted or unintended destruction of valued magnetic tape files.

Communication between the input/output controller and the various sources is by means of CPU registers, flag setting and software registers which contain codes for the unit number and read or write operations commanded.

As previously mentioned, the preferred editing system can at any time exist in one of three basic modes: keyboard, input, or output. While the operator is programming the input/output controller, the system remains in the keyboard mode. Once, however, the operator relinquishes control to the input/output controller and the screen executive begins processing, the system is switched into the output mode. Thereafter the system exists alternatively in the output and input modes as directed by the screen executive. During input/output processing all of the system keys on the keyboard are disabled except for the attention key of the system control keyboard which may be struck to set a panic flag. The screen executive continuously checks for the panic flag and immediately changes the source to keyboard and the mode to the keyboard mode whenever the panic flag is encountered. So long as the panic flag is not encountered, the screen executive will continue to direct the input and output of data until processing is complete.

1. Input/Output Command Language

In the preferred system I/O sequences are defined by means of command statements entered with special command keys which are located in the system control keyboard. When these keys are struck, the FSM sets command flags in a special memory area. These flags designate which peripheral devices, if any, are enabled for input and output. They also designate whether certain modifying routines are to be performed including: the code search routine, job/take search, clear text routine, and input or output to cursor. One key, called the enable key, is reserved to signal the end of a string of command keystrokes.

In the preferred system, the keyboard size is reduced by programming the command keys for more than one use. The flag which is set by a command keystroke depends on which prior command keys have been struck. Thus the operator must follow an established syntax when forming the command statement. One logical syntax is to group device and modifier commands together with the operation, input or output, which they define. An example of such a command syntax is shown below:

[<"Input", Device> <Modifiers>]

[<"Output", Device> <Modifiers>]

[Enable]

The device flag is set by striking one of the "mag" keys or a "paper" key. The modifiers are optional and can be some combination of the clear text routine, code search routine, job/take search routine, and cursor routines. The enable key closes the statement. In the preferred system all input and output procedures use the screen as either the object of input or the source of output. For this reason it is convenient to design input/output command language such that is either the input or output phrase is missing from the command statement, that the scroll memory buffer is automatically chosen as the appropriate input or output device by default. Thus in the example syntax shown above, the statement: [<"Input", Device> <Modifiers>] [Enable] indicates that input data from the assigned input device are to be stored in the scroll memory.

a. Input Search

If the "search" modifier command is included in an input command statement, text material on the selected input device will be searched during the course of input operations for a defined character string until the search argument is found or the entire text string has been input. This process is described above in conjunction with the CRT screen manager and is illustrated in FIG. 23. A search may "destructive" if material is discarded from the top of the screen until the argument is found or non-destructive if it is merely part of a throughputting operation.

b. Mag Tape Positioning

If the job/take search modifier command is included in the command statement input phrase, the tape will be positioned at the job and take location selected by the operator. When this command is used, the operator must provide additional keystroke information to identify the chosen job/take location.

A command may be provided which will allow the operator to specify a job/take location to be the stopping point of a reading operation. It is also convenient to provide a rewind command to cause the tape to be positioned at the beginning of the file.

FIG. 24 illustrates in flow diagram form the job/take search operation. When the job/take search is included as a part of the input command phrase, the job/take search routine first checks the job number register of the specified mag unit. Depending on the information stored in this register the job/take search routine determines whether the tape is located before, after or at the job specified in the command statement. If the tape is at a position ahead of the job specified, a forward job search is initiated, and continues until the specified job is located on the tape. When the tape reaches the specified job, the routine returns via loop 1 to the entry point. In a similar fashion, if the desired job is located ahead of the current tape position, the job/take search routine commands a reverse job search until it arrives at the location of the requested job. When the tape reaches the specified job, the routine returns via loop 2 to the entr