FR2533721A1 - COMPUTER SYSTEM WITH REAL-TIME COMPILATION - Google Patents

Abstract

THE INVENTION RELATES TO A COMPUTER SYSTEM ENSURING THE COMPILATION IN REAL TIME OF AN ORIGINAL PROGRAM IN LANGUAGE EVOLVED AT THE TIME IT IS ENTERED OR REVISED AT THE DESK. FOR THIS PURPOSE, THE COMPUTER INCLUDES A COMPILER PROGRAM, AN EDITOR PROGRAM AND AN ORIGINAL CODE BUFFER MEMORY. A PAUSE MARK CHARACTER IS RECORDED AT THE BEGINNING OF THE BUFFER MEMORY AND PREVENTS THE COMPILER FROM MOVING BEYOND. WHEN CHARACTERS ARE ENTERED AT THE KEYBOARD, THE EDITOR TAKES CONTROL OF THE SYSTEM AND SAVES THESE CHARACTERS INTO BUFFER MEMORY UNTIL A CART FEEDBACK IS ENTERED. AT THIS TIME, IT REPLACES THE PAUSE MARK WITH A SPACING AND SAVES A NEW PAUSE MARK IN THE LOCATION ADJACENT TO THE RETURN OF THE TROLLEY. THE COMPILER CAN THEN CARRY OUT THE LEXICAL, SYNTACTIC AND SEMANTIC ANALYSIS OF THE LINE WHICH JUST BEEN WRITTEN, UNTIL THE NEW BRAND OF PAUSE.

Description

The present invention relates to computer systems.

  and more particularly to a new computer architecture which ensures the compilation in real time of an original program evolved at the same time as the program is entered or revised at the desk by the programmer. Since men write programs in

  a programming language and that computers do not

  cutent than machine language, it is frequently necessary to translate from one language to another When the programming language is "advanced", that is to say abstract in the sense that it does not handle explicitly

  registers and other computer hardware, translation

  tion of the original program is executed by another program called a "compiler" The original programma is called a "source code" and the resulting translation of the program is

called the "resulting code".

  In addition to translation, the compiler must also perform lexical, syntactic and semantic analyzes of the original code. Lexical analysis is performed by a

  "explorer" and this is the process of forming a se-

  quence of bytes of original code in symbols or signs,

  somewhat like the formation of a sequence of.

  characters in English words These symbols are then subjected to syntactic analysis by a syntactic analyzer called

  a "perser" which determines if they are arranged in a rela-

  tion that conforms to the rigid grammatical rules of the programming language Semantic analysis determines whether symbols conform to additional rules that cannot be conveniently expressed by grammar

of language.

  These analyzes are very similar to a syntactic analysis.

  tick of words in an English sentence If the sym-

  boles violates a syntactic or semantic rule, we say

  that an "error" has been committed and the compiler must find out

  train the programmer by issuing an "error message"

  sible. After translation, the resulting code is usually "chained" and "loaded", a process in which it is joined with other modules in resulting code to form a program in machine code com Dlet which can be executed because

the machine.

  In recent years, the sharp increase in software costs, the lack of specialized programmers,

  the rapidly expanding computer market, widespread adoption

  widespread use of microcomputers and the under-utilization of a large part of the available hardware due to a lack of software have forced the adoption of advanced languages and the undertaking of concerted efforts to make their use

more efficient.

  However, programming in an advanced language is still a slow, tedious and ineffective process. For example, even under the optimal conditions of an interactive console, a compiled language requires the execution of a sequence of repeated steps which include loading of the editor, writing or revising the original code, loading the compiler, running the compiler, loading the link editor, running the link editor, switching to program and repeat machine

  of the sequence when an error is indicated during the comp

  breaking the original code or executing it: the resulting code.

  For a large part of the time, the programmer is obli-

  ge to wait for the completion of loading or execution steps

  cution and this waiting time is a waste while

  being tedious As a result, the programming process

  Mation is slow and expensive It is generally accepted that the production of the average professional programmer is only five to ten lines of original code developed per day (Doc n '4) The mentions in parentheses refer to the

  bibliography given at the end of this description.

  The recent widespread use of home microcomputers has greatly increased the difficulty of the problem of

  programming Most users who currently write

  Programs for such computers have not received professional programmer training and are reluctant to waste time, effort and endure the boredom and frustration inherent in the mechanics of programming in a language compiled with the systems

  of current microcomputers (Doc N O 9).

  Instead, the majority of computer programmers

  domestic workers use BASIC interpreters These

  the latter are generally syntactically poor, ineffective

  caces to reveal errors, unable to use local variables, unable to pass parameters to subroutines, unable to call subroutines by name, unable to link library modules, and

  they lack both data structures and struc-

  data flow control tures so that it makes it extremely difficult to write an error-free program for any but the simplest applications BASIC is therefore considered to be a very poor means of teach good technique of

  programming (Doc n 1) These BASIC interpreters are also

  so slow in execution that they are also disadvantaged

  gaseous or even unusable for many applications.

  However, the mechanics of compiling with sys-

  of modern microcomputers is so inconvenient that BASIC interpreters predominate in the field of microcomputers and considerably degrade the process

programming.

  Many attempts have been made to

  reduce the disadvantages of conventional use of

  pilators One such method is the so-called "incremental" compiler

  "(Doc # 5, 6, 7, 10, 11) o When each line of original code is entered at the desk, it is analyzed to determine if it conforms to the syntax rules of a restricted local grammar, in which the line is treated in isolation without taking into account the context of the whole program If the line is free of error from this angle

  limited, the programmer is free to enter the next line.

  Otherwise, an error message is displayed and the error must be corrected before new lines are entered. After the whole program has been entered, the program is subjected to new syntactic and semantic analyzes with regard to the context-dependent rules after which the resulting code generation and execution can be performed. The incremental compiler has certain advantages when used with languages which have few context-dependent limitations, such as BASIC For modern structured languages, such as Algol, Pascal PL / 1, C and l 'Ada, the read local analysis that can be performed after entering each line is only a relatively small part of the total analysis required and

  does not justify the corresponding overhead.

  Another well-known method of the prior art has been called "repeated recompilation" (Doc n 2) In this solution, the syntactic and semantic analyzes carried out after the entry of each line include all the context-dependent rules and take into consideration the entire partial program entered up to this point Therefore,

  even when a single multiplet of the original code is revised

  gine entered, the entire original program must be re-

  compiled from the beginning Since this recompi-.

  lation must be completed before new lines

  can be entered, the important system time of this

  rhode prevents its use except for the shortest programs.

  In an effort to avoid time-sys-

  teme of recompilation completes a number of meta

  partial recompilation methods have been devised (Doc.

  3 n 1, 3, 8) These methods generally required the use of

  use of a complex data structure for the code of-

  rigine and / or a complex editor that are such a pro-

  grammer with sufficient method skills

  particular can make a change in the code of-

  rigin so that it is only necessary to perform

  kill a recompilation of the modified part of the original code

  gine These solutions require the use of an excess quantity

  computer memory and / or highly skilled

of the programmer.

  These prior art methods have had no

  practical application except as curiosities experimen-

  tales in pure search The commercially available compilers still require the repeated sequences of the loading, editing, loading, compilation, loading,

  connection and machine passage, as described above.

  The ideal architecture for the programming function should have the following characteristics: compilation should be performed in real time

  when the original code is entered or revised by the program-

  dies; the system should be able to use modern block-structured language with powerful syntax, such as Algol, C, Pascal or PL / 1; there should be no waiting for access to the discs while writing, reviewing or compiling the program except to the extent necessary for the initial entry or saving of the original code files; an error message should be displayed almost instantly after a syntax error has been entered at the desk; correction of original code errors should

  be quick and easy without reloading the file editor

  shit original code or compiler; compilation should be completed almost immediately after entering the last line of an original program without error;

  compilation should be complete in the sense that

  no other syntactic or semantic analysis should be necessary and that the absence of an error message should

  ensure that the program does not contain syntax errors

tick or semantic;

  the programmer should be able to stop at any time

  ment the execution of the resulting code, to examine the values of all the variables and to continue the execution, all this without requiring the prior insertion of writing instructions, break points or other focus code in the original program; and architecture should not impose any additional conditions relating to the law of a syn-

  tax of particular peculiar language, of an editing mechanic

  complex or demand special specialization of the

programmer in the method.

  The following is a summary description of a

  preferred embodiment of the invention.

  The programmer calls the integrator-editor system in real time by typing his command file name on the keyboard of the console The command file containing the

  part of the system software is then loaded into the

  moire from disk o-code buffer

  rigine, a region of memory which must contain the original code, is initialized so that the first byte it stores in memory is a predetermined code which will be

  called a "Pause Mark" Running the compiler com-

  then begins by reading the "Pause Mark" as a character found in the first location of the buffer When the compiler reads the "Pause Mark", it repeatedly enters an infinite loop reading the same location until the contents of this

  location be changed by the editor to a blank (space-

  is lying). When the programmer hits a key on the keyboard

  of the console, the central processor executes the sequence of in-

  next terruption, described for an 8080 microprocessor

  or Z 80 After completion of the instruction being executed

  tion, the processor enters the interrupt mode and communicates its new state to the system by emitting a signal

  acknowledgment of interruption.

  Upon receipt of this signal, the interrupt equipment

  transmits an RST instruction on the data bus The pro-

  stopper then executes the RST instruction which is a call to a byte at a location chosen in the lower part of the memory where a jump instruction ("vector") is stored in the interrupt service routine which

includes the editor.

  The interrupt service routine firstly backs up the stack pointer and other registers of the unit.

  processing tee If the key hit corresponds to a character

  alphanumeric or other character that is not a character

  control character, this character is placed in the second place

  cement the original code buffer immediately after the Pause Mark The buffer pointer is then advanced to the next location, the registers

  the unit are restored, the processing unit is switched on

  interruptible status and 'RET (return) instruction is executed

  to return the command to the compiler.

  The compiler continues to execute its infinite loop in which it repeatedly reads the Pause Mark character contained in the first string of the original code buffer This sequence is repeated when the programmer hits new keys on the

  keyboard, successive characters being entered in em-

  successive placements of the original code buffer as the buffer pointer advances This sequence continues until a corresponding key

  to a command character be struck.

  If this command character is a carriage return,

  the corresponding code (13) is entered in the memory-

  buffer, the buffer pointer is advanced, the Pause Mark code is then entered in the buffer location adjacent to the carriage return code and the initial Pause Mark code contained in the first location is replaced by the code (32) representing a white space The location of the Pause farque has thus

  been moved from its original point and put at the end of the first

1st line of original code.

  After returning to the compiler from the interrupt service routine, the compiler pointer goes to the first location in the buffer and reads the code representing a spacing instead of the Pause Mare

  compiler then advances its pointer repeatedly

  tive to the next memory location and performs its ana-

  Lexical, syntactic and semantic lyses on the first line of original code contained in the buffer The compiler can either display an error message or issue a compiled summarized code, as the case may be, until the pointer to the compiler reaches the new Pause Mark introduced at the end of the first line of the code

of origin.

  When it reaches the new Break Mark, the

  again enters an infinite loop without advancing its pointer until the editor moves the Pause Mark to the end of the next line after which the compiler is free to compile this

next line of original code.

  Command characters can be entered

  other than a carriage return by hitting the keys

  properties for performing the classic editing functions of a screen editor For example, you can correct

  errors in the line in progress with the original code being moved

  erasing the cursor backwards This has no effect on the com-

  pilator who cannot advance beyond the Mark of

  Pause located at the end of the previous line.

  However, if by hitting the appropriate command key

  requested we cause the cursor to move up one or more lines to a location before the Pause Mark, this activates an Indicator

  Recompilation in order to enter a recompilation mode.

  In this case, following the return of the order to the compilation

  the latter is re-initialized so that it can re-

  compile the original code from the very beginning of the

  original buffer moire Revisions or insertions of

  The following original text results in the editor de-

  places the Pause Mark to an update location adjacent to the end of the line before the line

most recently revised.

-33721

  When the compiler finds a syntax error in

  the original code, it displays an error message The pro-

  grammer can then revise the original program to correct

  Manage the error After returning from the editor, the compiler is re-initialized to recompile the original code. The original code entered and the resulting code sent are preferably stored in the central memory of

  so that accesses to disks do not hinder

  excessive editing and compilation processes.

  If the original code or resulting code buffer

  is full, its contents can be stored in a file

  shit on disk in the classic way used in editors and word processors such as CP / M ED and Wordstar The use of memory selection systems or the arrival on the market of 16-bit microprocessors with their advantages large memory spaces will avoid the

  need for disk storage until the compi-

  lation be finished Other features of the invention will appear

  on reading the description which follows and examining

of the attached drawings in which:

  Fig 1 is a block diagram which represents the.

  relationships between the main elements of the material which

  titue a preferred embodiment of the computer system according to the present invention; Fig 2 is a diagram showing the logic and hardware interrupt circuits of the system; Fig 3 is a flowchart showing the general sequence of operations; Fig 4 is a flowchart showing the sequence of operations of the compiler; Fig 5 is a flowchart showing the sequence of editor operations; and Fig 6 is a flowchart showing the sequence

  operations of the control character routines of the e-

editor.

  A detailed description of a mode will be given below

  preferred embodiment of the invention The details described are merely illustrative of one of the many forms

  under which the invention can be implemented The

  vention and the novelty do not reside in the hardware or in the software considered separately but rather in a

combination of the two.

  In Fig 1 with the arrow we will first refer,

  the main material elements have been represented

  kill the entire system of a preferred embodiment of the present invention Each element will be designated by

  the inscription written in the respective rectangle of the drawing.

  The CATHODIC TUBE DESK refers to an appropriate terminal

  any required including a keyboard for entering the original code to be compiled and also for entering

  of revision commands used to change the code Le ter-

  minal also includes a video display to allow

  using a screen editor The keyboard is preferably

  rence, integral with the video display to form a unitary console having an RS-232-C serial link with the rest of the

system.

  This serial link is connected to the ACCESS POINT

  INPUT which is preferably made up of an ERAS (

  universal asynchronous receiver-receiver) such as, for example the 1602, the AY5-1013 or the TMS 5501 Each keystroke on the keyboard of the cathode ray tube console results in the serial transmission to the ERAS of a train of constituent bits

  the byte of the ASCII code corresponding to the key hit.

  ERAS reformats the bits into this byte which is then trans-

  paralleled on the data bus to the processing unit accumulator (UDT) ERAS also forms an output access point The execution of an OUTPUT command by the processing unit is effect the transmission on the data bus of a byte from the accumulator to the ERAS aui can then transmit the byte in series to the DESK A

  CATHODIC TUBE for display on the video screen.

  In the usual operating mode of a micro-

  conventional computer, the state of the entry access point is repeatedly checked by the processing unit in a selective call loop until the state of the entry access point indicates that a byte of data has been kept and is available in the register of data received D of i'ERA So The present invention uses instead of this

  mode, a mode of interruption of operation by means of-

  which processing unit normally performs the compilation

  tor until ERAS receives a byte from the CATHODIC TUBE DESK The compiler is stored in an area of the main memory designated COMPILER on

Fig 1.

  The line of data available from ERAS is then

  high level and this in turn activates the CONTRO-

  THEIR INTERUPTION to cause the execution, by the processing unit, of the editor The latter is stored in an area of the main memory designated EDITOR on

  the drawing After entering the character received in MEMORY-

  ORIGINAL CODE BUFFER formed in main memory

  or after completion of an editing order, an instruction

  return (RET) is executed by the processing unit to cause it to resume execution of the compiler at

  from the point where it was interrupted.

  When the COMPILER is executed, it performs,

  preferably lexical, syntactic and semantic analyzes

  ticks of the original code of the program stored in the ORIGINAL CODE BUFFER MEMORY In a preferred embodiment, the COMPILATOR also issues a resulting code and

  puts it in memory in the Ml EMOIRE-PAMPON OF RESULTING CODE.

  After completion of entry and compilation of the

  gram in original code, ordering the processing unit-

  may be transmitted to the INTERPRETER for execution of the resulting code if the latter is in the form of a code

  intermediate The option can be offered to the programmer from -

  save the original code and / or the resulting code in a secondary memory, such as a disk or tape medium. Instead of generating an intermediate code ("p code"), the COMPILATOR can be of the type which transmits executable machine codes The COMPILER may require only one pass of the original code in the manner of the Pascal cor mpiler

  usual recursive descendant If the COMPILATOR requires more

  If there are several passages, the first passage should preferably perform the syntactic analysis so as to reveal all

errors get syntax.

  The interrupt system allows the programmer to stop

  ter execution of the program in machine code at a given time

  born any, examine the values of the variabies, then continue execution No additional hardware is required for this additional function and software

  extra required is very unimportant.

  In Fig 2 to which we will now refer, the circuits and the elements of the material which are shown

  intervene directly in the interruption operation.

  When a key on the CATHODIC TUBE is hit, a train of pulses constituting the multiplet corresponding to

  the key pressed is transmitted by the exit access point

  tie S series of RS-232-C A converting door C 1 conver-

  tit the pulse train from RS-232-C levels to levels

  TTL (transistor-transistor logic) to meet the conditions

  The access point EN of the ERAS This transforms the train of successive pulses into a byte of eight bits (byte) which is stored in the register of data received from the ERAS The latter emits then a data signal available on a DAV pin, signal which is

  transmitted by a door G 1 to a vector interrupt input

tors VI of the PRIORITY ENCODER.

  Although only a VI input pin of

  this encoder, it is understood that this chip includes

  carries other vector interrupt input pins to which other switch devices can be connected.

  The PRIORITY ENCODER arbitrates requests to interrupt D-

  competing tion applied to its inputs and determines

  that it is the request which has the highest priority.

  The EI input to activate the P Ri ORITE ENCODER is

* grounding, as shown.

  If it is accepted that the request to interrupt the DESK and the ERAS is recognized as priority, the ENCODER transmits

  then a three-bit code A 0, A 1, A 2 at the respective inputs

  INTERRUPTION VECTOR REGISTER tives The other five entries in this register are kept positive by a voltage source + V so that the resulting byte applied to this register chip constitutes an RST call instruction The signal product on the output pin GS of the PRIORITY ENCODER is transmitted by a door G 2 to the lock activation input LE of the INTERRUPTION VECTOR REGISTER to cause storage

  by the latter of the RST call instruction in its bas-

internal bistable cules.

  Activation of the output pin GS of the ENCODER

  PRIORITY also transmits an interrupt signal by

  via an AND gate A 1 to the interrupt request pin INT * of the ZSO processing unit If it is assumed that the interruption of the processor is authorized, after completion of the instruction-in progress , the status pins IORQ * and M 1 * of the processing unit are made active and their signals are transmitted by gates G 3,

  G 4 at a gate A 2 to form the INTA signal (AR interrupt-

  tion) This last signal is inverted by a gate G 5 and ap-

  folded to the OE pin for activating the output of the INTERRUPTION VECTOR REGISTER after which the RST call instruction applied to the inputs of this register is loaded

on the DATA BUS.

  The RST instruction is then entered in the processing unit Z 80 which executes it, which has the effect that it drives back the content of the program counter in the stack and that it jumps to a predetermined location of the lower part of the memory This location contains a "vector"

  or jump instruction (JMP) from three bytes to one wheel

  tine of service of interruptions This last contains the editor as well as a subroutine to put in memory

  the contents of the registers of the processing unit

  ande of the processing unit is then kept by the editor

  until a character has been entered into memory-

  original code buffer or an edit operation has

been completed.

  The editor includes an input instruction which, when executed, has the effect that the processing unit

  places the address of the ERAS access point on the BUS D'A-

  DRESS This address is verified by the COMPARATOR and if

  it corresponds to that of the access point, the output pin

  tie EOUT is made active to signal it to DECODER This

  the latter is controlled by other control and

  tat (not shown) in the conventional way so as to transmit an RDE * signal to the corresponding RDE input of the ERAS The byte contained in the register of received data (not shown) of the ERAS is then applied to the BUS DATA and transmitted to the accumulator which is part

of the processing unit.

  In the preferred embodiment of the invention

  presented in Fig 2, the integrated circuits used

may be as follows.

ERAS: 1602

PRIORITY ENCODER: 74 L 5148

  INTERRUPTICN VECTOR REGISTER: 74 L 5373

DECODER: 74 L 5155

COMPARATOR: 25 L 52521

C 1: 1489

C 2: 1488

  In Fig 3 to which we will now refer,

  the general sequence of system operations has been shown

  tome The COMPILATOR normally holds control of the processing unit and is either in an infinite loop

  after reaching a Pause Mark in the memory-tam-

  pon of original code is analyzing the code from-

  which is in the buffer.

  When there is a KEY STRIKE on the termi-

  nal, this causes an INTERRUPTION as a result of which the-

  computer is sent to the interrupt service routine.

  The latter includes a subroutine to execute the

  operation SAVE THE REGISTERS indicated on the drawing.

  The EDITOR is then executed by the processing unit.

  If the KEY STRIKE corresponds to a command character, an editing procedure, such as moving the cursor, scrolling the image, on the screen, deleting a character or deleting a line, is performed If the KEYKEY matches an alphanumeric or other valid origin code character, the original enter code buffer is displayed on the video screen and the screen cursor is advanced to the position

next character.

  The interrupt service routine then performs

  a jump to its subroutine to perform its RESTAU-

  RER THE REGISTERS by means of which the registers of the

  treatment nity are returned to their original values they

  had at the time of the interruption.

  The instruction AUTHORIZE INTERRUPTIONS (El) is then

  executed by the processing unit so that this aer-

  can respond to the next interruption Finally, the ins-

  RET truction is executed so that the computer can

  RETURN TO THE COMPILER The compiler then resumes the exe

  cution to the point where it was interrupted.

  In Fig 4 to which we will now refer, the sequence of operations of the compiler has been shown.

  initialization, the compiler first performs its function

  tion READ CHARACTER by means of which the byte contained

  in the first location of the o-code buffer

rigine is read.

  If this byte is the predetermined code designated Pause Mark, the pointer of the compiler does not advance and the compiler enters an infinite loop in which it continues to read the same location until the content is changed to a blank by the editor When this

  change occurs, the compiler memory poihntor

  tor is incremented at the next location in memory-

  buffer so the compiler comes out of its Pause loop

  comr e indicated by the inscription ADVANCE MEMORY POINTER.

  As indicated by the inscription'SYMBOLE? ", the analyzer

  the lexical of the compiler then determines if the character of ori-

  gine lu constitutes the last character of a symbol, such as an identifier, an operator or a punctuation mark If not, the GET CHARACTER function is

  again executed until a symbol is recognized.

  The compiler syntax analyzer then determines whether this symbol conforms to a CORRECT SYNTAX in accordance with the grammar of the programming language If the symbol

  does not conform to the syntax, an ERROR MESSAGE is displayed

  plug. If the syntax is correct, the READ CHARACTER function is repeated until an error is found or the END OF THE PROGRAM is reached In this case, the CODE GENERATOR can be called if this function is executed in the form of a separate passage Alternatively, the generation of the code can be carried out concurrently with the lexical and syntactic analyzes The generated code can then be

  stored on disk and / or executed, at the option of the pro-

  grammer, as indicated by the inscription SAVE / -EX 4 CU-

TER RESULTING CODE.

  For the clarity of the illustration, we will show how

  the simple and widely published PL / 0 compiler of the pro-

  N Wirth spanker (Doc N 12) can be modified to put

  of the present invention In the description which

  the following identifiers have been added which do not appear

  not appear in the original PL / 0 compiler as published. CONT, PEEK, RECOMPILE, PTR, PM and SP The first instruction in the modified compiler is:

IF NOT CONT THEN

  The Boolean variable CONT is FALSE on initial entry into the compiler, which means that it is not a continuation of a previous execution.

  terms, the compiler has just been entered for the first

  first time during this session The following assignment instructions are therefore executed to initialize the contents of the W ORD, WSYM, SSYM, MNEM 1 ONIC tables, DECLBEGSYS, STATBEGSYS and FACBEGSYS shown on pages 346,

  347 of the Treaty of Wirth (Doc n 12) The values of these ta-

  remain fixed during the whole execution of the compiler

  and the IF conditional statement above avoids the need for

  re-execute all of these ins: ructions in assignment to

  The rest of the re-initializations of the compiler for recom-

  pilations In other words, after the first check

  of the variable CONT, this one is set to TRUE so as to con-

  then rotate the assignment instructions when a re-

compilation is required.

  After the conditional block for assigning arrays, a PEEK assembly language function is called to

  read the contents of the memory location above immediately

  the start of the original code buffer,

  location in which the Recompilation Indicator is contained

  If, in this location, the ASCII code representing the letter "R" has been loaded by the editor, a procedure of the RECOMPILE compiler is called to re-initialize the variables ERR, CC, CX and LL and to assign the value to

  constant AL (10) to the variable KK.

  The RECOMPILE procedure also puts the value of a

  PTR pointer variable equal to the start address of the met

  original code buffer The PTR pointer is the point

  memory of the compiler lexical analyzer and it is successively advanced byte by byte of the original code to read the latter the lexical analyzer reads the byte contained in the memory location designated by

the PTR pointer.

  The lexical analyzer also includes another modification

  important cation of the PL / 0 compiler This modification is included in the GETSYM procedure in which is also

nested the GETCH procedure.

  GETSYM has as its first instruction:

WHILE CH = '' EXECUTE GETCH;

  This is part of an infinite loop that repeats as long as the GETCH procedure returns the ASCII code (32) which represents a spacing As explained above, the GETCH procedure returns the spacing code 32 each

  once she reads the Pause Mark.

  The first instruction of GETCH is:

CH: = PTR-;

  so as to load the contents of the job into the variable CH

  placement of the original code memory designated by the va-

  riable pointer PTR The following instruction of the GETCH procedure is:

IF CH = CHR (PM) THEN

  thus checking if the byte read is the PM Pause Mask which is a constant equal to 35 We chose this value since it is a visible character and it was not

not otherwise used.

  The following statement follows the SI clause:

CH: = CHR (SP)

  in which SP is equal to the ASCII code (32) for a space-

  The command then returns to GETSYM in which the condition of the clause WHILE THAT is satisfied so that it calls the GETCH procedure again This sequence is repeated and results in an infinite loop as long as the byte contained in the location of memory that is read

is the Break Mark.

  After the editor has replaced this Pause Mark multiplet with the ASCII code representing a spacing, the loop is interrupted because the Boolean condition of the SI clause is no longer satisfied (the variable CH is not equal Instead, the following ELSE clause is executed to advance the PTR pointer from the original code memory to the following memory location by the instruction:

PTR: = PTR + 1;

  after which the next call to the GETCH procedure reads the job

  next cement from the original code memory, to allow

  put the compiler to continue its advance through the original code the PTR esz pointer advanced repeatedly

  each time you call the GETCH procedure until it has

  the new Break Mark introduced by the publisher,

as described below.

  In Fig 5-to which we will refer, we have represented

  The editor's sequence of operations The ENTER CHARACTER function is first executed in response to CHARACTER HIT (Fig 3) The editor then determines whether

  the byte entered is an ORDER CHARACTER In the ne-

  gative, the character is entered in the original code buffer, as indicated by the inscription CAR IN

  MEM-BUFFER The entered character is also displayed on the display.

  notch as indicated by the inscription CAR TRANS A ECRAN PU-

  PITRE If the character entered is a control character,

  the editor then determines whether it is a RETURN FROM CHA-

  RIOT? If not, the routine of the editor - appropriate for processing the command characters is called, as indicated by the inscription TRANSF A ROUTINE CAR DE COM and

  as will be described below with reference to Fig 6.

  As shown in Fig 5 to which we continue-

  ra to refer, if the character entered is a return of the

  cart, a new Break Mark is written in the

  original code buffer in adjacent slot

  at the end of the current line, as indicated by the inscription-

  tion INSERT NEW PAUSE MARK The old Pause Mark is changed to a blank (spacing) as shown

  by the inscription REMOVE OLD PAUSE MARK.

  To facilitate the subsequent location of the location-

  Pause Mark, a memory word location

  is reserved as a Pause Register to highlight

  moire the address of the Pause Mark location The

  of the new Break Mark is thus set

  moire in this memory register, as indicated by the inscription UPDATE PAUSE REGISTER The ASCII code representing a carriage return (13) is then entered in

  the original code buffer in the adja- location

  cce at the Pause Mark, as indicated by the inscription o INSERT CAR IN MEM-BUFFER The ASCII code representing a line advance (10) can be entered after the return of the

  cart, if this convention is desired.

  In Fig 6 to which we will now refer, we

  represented the sequence of operations of the routines of the

  editor to process the characters of co Lmmande entered in the pu-

  pitre The character entered is first checked to

  finish if it is the code corresponding to the CURSOR RISE operation If not, a check is

  then performed to determine if it is the corresponding code

  during the IMA GE BACKUP operation (towards the start of the program, which in practice corresponds to a scrolling of

  image down) If not, the character of com-

  Mande is treated in the conventional manner which will not be described further, as indicated by the inscription TREAT OTHERS

ORDER CHARACTERS.

  If the command character entered is the code that represents

  feel the CURSOR UP or the one representing the PICTURE RISE, the respective operation Raise the CURSOR or SCROLL THE IMAGE is executed In the first case, the

  cursor is moved up one line on the video screen.

  In the second case, the screen is cleared and rewritten to display

  expensive lines from the original code buffer which

  immediately precede deleted lines.

  As indicated by the inscription ENTER NEW PAUSE MARK, a new Pause Mark is introduced at the location immediately adjacent to the end of the line of the original code buffer preceding the line which carries the new position of the cursor The operations REMOVE OLD PAUSE MARK and UPDATE REGISTER

  OF PAUSE are then carried out in the manner that has been

  above, referring to Fig 5.

  The operation SET RECOSMPILATION INDICATOR causes

  re-initializing the compiler when the latter

  takes control of the processing unit after the return of the interrupt service routine This indicator is preferably a location of the memory in the only

  a predetermined code can be loaded to inform the compi-

  reader that a recompilation of the original code is required.

  In the preferred embodiment, this recompilation indicator is required to require a recompilation each time the cursor is moved up or the image is raised. In other words, it is accepted that each time the cursor is moved to indicate an original code which may have already been compiled, this code will be

  changed to require recompilation.

  Another method would be to put the recompilation inducer only if the code previously compiled is

  actually changed since the pro-

  gralleur scrolls the image in one direction then in the other

  without making any changes to the original code.

  Yet another solution would be to create in the

  memory a register which would contain the address of the last

  position of the compiler pointer The editor could

  then compare this address to the memory location-

  original code buffer designated by the cursor to determine

  undermine if editing changes are being applied

  pcrtés to an original code that has already been compiled.

  Although these other methods result in a smaller

  number of recompilations, the preferred embodiment pre-

  feels the advantage of a simpler implementation In addition, the recompilation process is so much faster than

  manual entry of the original code on the console that the

  pilateur will be able to recompile all the program and catch up with the programmer before the latter has had time to type more than a few new lines of code except in the case of

  extremely large programs Therefore, the reduction

  tion of the number of recompilations to the absolute minimum is

not essential.

  The editor is written in Pascal with calls to sixteen

  procedures and functions in external assembly language.

  We will now describe those of these routines which are clean

to the present invention.

  When entering the editor, the bool enne ECONT variable is checked to determine if this editor call

  is the first entry in this session or a conti-

  nuation If the variable ECONT is FALSE, it is then set to TRUE and the following procedures: INIT, NEWFILE, VECTOR and

TOPLO are executed.

  D The INIT procedure resets the code buffer to zero

  original, puts the memory pointer at the beginning of the memory

  pad, introduces the Break Mark in the first place

  buffer, puts the contents of the Pause Log

  equal to the address of this first location, initializes the cur-

  in the first row and in the first column of the screen and places the recompilation indicator pointer

  that it designates the location of the memory which precedes the first

  mier byte from the buffer.

  The NEWFTILE procedure prompts the programmer to

  choose either a new file for entering the Code of Ori-

  gine is an old file for executing a revision.

  In the latter case, the file is loaded into memory-

  original code buffer from disk and first

  original code screen image is displayed.

  The VECTOR procedure calls the assembly procedure

  external POKE three times to store in the

  low memory link (20 H) the jump vector to a sub-

  SAVREGS routine which stores the contents of the registers

  of the processing unit In response to an interrupt

  due active by pressing a key on the pu keyboard

  pitre, the processing unit executes the RST 4 call instruction and executes this jump vector then the SAVREGS subroutine After the registers have been saved, a jump instruction contained in the subroutine sends

  the processing unit to the editor.

  The TOPL O procedure transmits the command to the PL / 0 compiler. It is usually called after the editor has completed entering the character or the editing function.

  corresponding to the key hit on the terminal keyboard.

  In this case, the procedure is called after initialization

* from the publisher.

  The following instruction from the editor is only reached when an interruption occurs in response to a keystroke. This instruction loads the ASCII coda entered from the register of data received from ERAS into a variable. input is checked to determine

  v if it is a command character or an al-

  ph-anuric (greater than 31) In the latter case, the multi-

  plet entered the origirm code memory and

  displayed on the video screen in the conventional manner.

  If the byte entered is either the control code to move the cursor down or the command code to raise the image, the appropriate procedure is called and

  by the call to the UPDATE update procedure.

  The latter enters the original code buffer.

  gine a new Pause Mark in the location adjacent to the end of the old line in the case of a

  descent of the cursor and in the location adjacent to the end

  from the invisible line preceding the first line

  displayed in the case of an image descent operation.

  The UPDATE update operation also removes the an-

  this Pause Mark by replacing the Pause Mark

  held in the former location of the latter by the ASCII code which represents a space (32) in the Register

  is also updated at the location address

  ment of the new Break Mark.

  If the input byte is either the order code

  to move the cursor upwards be the code of com-

  request to raise the screen image towards the beginning of the original code, the corresponding procedure is called to perform the respective operation This procedure ends with the calls to the procedure previously described

  UPDATE update and also the RECOMPILE procedure.

  The latter stores the ASCII code representing the

  letter "R" in the memory location immediately preceding-

  the start of the original code buffer so

  lesson to build-the recompilation indicator above men-

  After completion of the recovery of the cur-

  the screen image, the processing unit

  returns to com Dilator cui checks the recommendation indicator

  pilation, determines that this indicator is set and then calls

  its Re-initialization procedure to constrain the compi-

  reader to recompile the original code from the start of the original code buffer. If the byte entered is the ASCII code that represents

  the return of the carriage (13), the CRET procedure is called.

  This routine enters a new Pause Mark in the slot adjacent to the carriage return code in the original code buffer, removes the old Pause Mark,

  updates the Pause Registry, and performs other functions

  more conventional, such as entering the line advance code in the buffer, updating the cursor and scrolling the video display if the current line is

the last line of the screen.

  It should be understood that the preferred embodiment described above and shown in the drawings has been

  given only as an illustration of one of the nom-

  breuse forms in which the invention can be implemented and that many modifications can be made to this embodiment by those skilled in the art without departing from the scope of reselling

appended cations.

  For example, instead of making the Pause Mark in the form of a predetermined code entered in a location

  of memory inside the original code buffer

  gine, the pause location can be defined for the compi-

  reader by a memory address contained in a register.

  The compiler can then be prevented from parsing the code

  stored in memory locations located above

  beyond this address which can be incremented and decremented

edited by the publisher.

  In addition, the interruption that causes the transfer of

  control of the compiler's processing unit from the editor

  The timer can be made active by a timer or clock instead of by the keyboard. In other words, the compiler can be interrupted periodically and the entry access point can be called selectively to determine if a key was struck If not,

  the interruption is completed and the command returns to the

  pilot If the selective call of the access point reveals that a key has been hit, the editor of the interrupt service routine takes the command and is executed in the manner

  which has been described above with reference to the mode of reaction

  preferred readout described For most applications, clock-driven interruptions at intervals of about 10 to 30 milliseconds should be frequent enough to stay at the typing frequency

keys on the keyboard.

  In addition, the recompilation indicator can be set

  each time the compiler determines that the code for

  gine contains an error In other words, we can ad-

  put that every time an error is revealed, the code

  original will be changed so that it will require a recommendation

  pounding. Another possible modification consists in removing the requirement of a recompilation from the very beginning of the original code in case the error occurs in the

  last completed line of original code During compilation

  lation of the line, the resulting register values, the

  entries in the tables, the handling of stacks, the a-

  variable assignments and entries in memory-

  code buffer are temporarily stored in memory and are not entered until the parsing of the original line of code is completed and determines that the line conforms to grammar If the line contains an error, these temporary entries are removed and the compiler pointer is brought back to the end of the previous line, thus avoiding recompilation However, this method still requires recompilation if the lines of code

  original lines preceding the last line are changed.

  Another possibility would be to advance the

  Pause mark by the editor after entering each character

  tere or after entering each delineate symbol This pre-

2,533,721 t

  would feel the benefit of revealing an error almost instantly

  when entering the keyboard The downside would be

  that recompilation would be necessary for all pe-

  tite fragpe errors without giving the processor the opportunity

  It is necessary to correct them before they are explored and analyzed.

syntactically lysed.

BIBLIOGPPHY

  1 L V Atkinson, et al., "Context Sensitive Editing as an Ap Droach to _ncrérmental Compilation", The Computer Journal, Tome 24, n 3, 1981, pages 222-229, Heyden & Son Ltd. 2 L V Atkinson and S D North, "COPAS A Conversational Pascal System", Softw- are Practice and Experience, Tome11, 1981, pages 819-829, John Wiley & Sons Ltd. 3 R B Ayres and R L Derrenbacher, "Partial Recompilation",

  Spring Joint Computer Conference, 1971, pages 497-502.

  4 F T Baker and H D Mills, "Chief Programmer Teams", Classics in Softwate Engineering, Published by E N Yourdon,

Yourdon Press, pages 195-204.

  L Bolliet, et al., "D 2 IA 2 'AG: A ulti-Access System for On-Line Algol Programming", Proc Spring JCC 1967, pages

547-552.

  6 P J Brown, "Writting Interactive Compilers and Inter-

  preters, Ch 2 4, pages 41-45, John Wiley & Sons.

  7 J Earley and P Caizergues, "A Method for Incrementally

  Compiling Languages with Nested Statement Structure ", Commu-

  indications of the ACM, volume 15, N 12, Dec 1972, pages 1040-

1044.

  8 K Lock, "Structuring Programs for Multiprogram Time-

  Sharing On-Line Applications ", Proc Fall JCC 1965, pages

457-472.

  9 J Pournelle, User's Column, BYTE, Sept 1982, page 324.

  J L Ryan, et al., "A Conversational System for Incremental Compilation and Execution in a Time-Sharing Environment", Proceedings Fall Joint Computer Conference,

1966, pages 1-21.

  11 S Sonderstrup and M Pelle, "COMAL-80 A New Language?",

  Dr Dobb's Journal, No. 56, Jiin 1981, pages 14-15, 46-47.

  12 N Wirth, "Algorithms + Data structures- = Programs", Ch 5, pages 280347, 1976, Prentice-Hall, Inc.

Claims (19)

  1 A microcomputer system for entry and com-   almost simultaneous real-time pounding of an original program, characterized in that it comprises: a desk for entering successive characters constituting the program   of origin; a semiconductor memory to store   moire the original program and a resulting program which   results from the translation of the original program, this   moire also containing a compiler and an interrupt service routine; a processing unit having an interrupt input, a program counter, a series   of registers and means operating in response to the acti-   Dption interrupt input to load into the pro-   gram a vector address which designates the service routine   vice of interruptions; said compiler holding normal-   the command of the processing unit to compile the partial original program as the latter has entered the memory; the compiler Understanding ways to translate the partial original program into resulting code and   to enter the latter into memory; functional means   in response to the operation of the console to make ac-   tive the interrupt input and pass, therefore,   the control of the processing unit, from the compiler to the rou-   tine of service interruptions; the interrupt service routine comprising means for storing in memory   the content of the registers; the service routine of interrup-   tions including an editor to successively enter the characters entered in selected memory locations   and to execute the editing commands; the editor includes   providing means for designating a location in the pro-   original gram stored, location where the compa-   guardian must take a break while waiting for the entry of a   other part of the original program; the compiler compre-   an execution loop, when the compiler reaches the designated pause location and which is executed until the location is changed; the editor advancing the pause location when additional parts of the original program are entered; the interrupt service routine comprising means for restoring the   original contents of the registers and to return the   request from the support unit to the compiler following   the completion of either the storage of at least one character   input either from the execution of an edit command.   2 A computer system according to claim 1, charac-   terized in that the editor includes means for modifying a part of the original program which was previously   compiled by the compiler; and means for re-initiali-   be the compiler in order to cause the latter to recompile the original program after said part compiled has been changed.   3 A computer system according to claim 1, charac-   Terérized in that the desk includes a display screen and a keyboard provided with keys; the editor with   selective means for displaying on the screen a selected part   the original program stored in memory;   a cursor to designate the location of the pro-   original gram which must be modified by the operation of the editor; means for moving the cursor on the screen in response to keystrokes of predetermined keys;   and hubs operating in response to displacement of the cur-   to move the pause location to a point before the location of the program designated by the cursor after the cursor has been moved up in   a direction corresponding to a return to the beginning of the pro- original gram.   4 A computer system according to claim 3, charac-   terized in that it comprises means for re-initializing the compiler in response to the movement of the cursor upwards, thereby causing the program to be recompiled by the compiler.   A computer system according to claim 1, characterized in that the desk comprises a display screen and a keyboard provided with keys; the editor with   means for displaying on the screen a selected part of the pro-   original gram stored in memory; a cursor   to indicate on the screen the location of the original program   cine which must be modified by the operation of the editor; means for moving the cursor on the screen in response to keystrokes of predetermined keys; turn means move the pause location to a point preceding the location of the program designated by the cursor after   the cursor has been moved up in a correct direction   responding to a return to the start of the original program; and means for re-initializing the compiler after the cursor has been moved up, thereby causing the   recompilation by the compiler of the original code.   6 A computer system for entry and compilation   in roughly simultaneous real time of a program, character-   terrified in that it includes-: a desk for entering characters-   successive tères constituting the original code of the program;   a memory to store the original code and also   also to store a compiler and an editor; the editor comprising means for successively entering the characters entered and for executing editing commands; a processing unit; the compiler normally having control of the processing unit for syntactically analyzing the partial original program stored in the memory; means for transmitting the command from the processing unit of the compiler to the editor; means to designate a location in the original program where the compiler should pause while   waiting for the entry of another part of the orientation program   gine; the compiler comprising means for pausing when the compiler reaches the designated location; means for advancing the pause location when additional parts of the original program are entered; and means for returning the control from the processing unit to the compiler after completion, either   the entry of at least one character entered, either ex- issue of an editing command.   7 A computer system according to claim 6, charac-   terized in that the processing unit comprises a series of registers; means to save the content of these registers when 2 a command is transmitted from the compiler   the publisher; and means to restore the contents of the   records following the return of the command from the editor to the compiler.   8 A computer system according to claim 6, charac-   terrified in this cue i 'idil Jeur cxrporte means to modify   the original code which previously was the subject of a za-   syntactic lysis by the compiler; and means for re-   initialize the compiler to cause the latter to recompile the original code after the analyzed code syntactically has been changed.   9 A computer system according to claim 6, charac-   terized in that it comprises: a display screen; means for displaying on the screen part of the original code stored in the memory; a cursor to designate on the screen the location of the original code which must be modified by an operation of the editor; means for moving the cursor on the screen in response to operation of the desk; and means for moving the pause location to a point preceding the location designated by the cursor after the cursor has been moved up in a direction   which corresponds to a return to the start of the orientation program gine.   A computer system according to claim 9, charac-   terized in that it includes means for re-initializing the compiler after the cursor has been moved up, thus causing the recompilation of the original code by the compiler.   11 A computer system for the roughly simultaneous entry and compilation of an * original code,   characterized in that it comprises: a memory having a memory   original code buffer; a keyboard; an editor for entering and reviewing an original code in the buffer;   a compiler to perform lexical and syn-   tactics of the original code when the latter has entered the buffer memory; actuable interrupt means for interrupting the compiler and for calling the editor in response to the actuation of the keyboard; limiting means to prevent the compiler from attempting to analyze the code beyond buffer locations determined by   the publisher; and means for returning the system order   teme a compiler following the completion of an edit function.   12 A computer system according to claim 11, ca-   characterized in that it comprises: a display screen; of   means for displaying part of the code of origin on the screen   gine stored in the buffer; a cursor to designate on the screen the location of the original code which must be modified by an operation of the editor; means for moving the cursor on the screen in response to typing of predetermined keys on the keyboard; and means for moving the pause location to a point preceding it   the location of the buffer designated by the cursor.   13 A computer system according to claim 11, ca-   characterized in that the limiting means include   means to identify a memory pause location-   original code stamp; a location where the compiler.   must stop until said identification is very   changed by the publisher; and means to advance the em-   pause placement after a predetermined amount of new source code has been added to the buffer so that the compiler can analyze the new source code.   14 A computer system according to claim 11, ca-   characterized in that it comprises: a processing unit having   a series of registers; means to safeguard the con-   kept records when the compiler is interrupted; and means for restoring the contents of the registers after the   return of the editor command to the compiler.   15. A computer system according to claim 11,   characterized in that it includes means for modifying a previously compiled part of the original code; and means to reset the compiler to recompile the   original program after modification of the previous part compiled from the original code.   16 A computer system for the almost simultaneous entry and compilation in real time of an original code, characterized in that it comprises: an editor for entry and modification of the code 'origin; a compiler that holds   normally the system command to process the code of origin-   gine except when interrupted; and means of return   to return control of the computer system, the   compiler, after the publisher has completed an operation   entry or modification of the original code.   17 A computer system according to claim 16, ca-   characterized in that it includes means for identifying a   pause point of the original code, location or the compa-   the author must stop until the said identification has been changed; and means for advancing the pause point after a predetermined amount of new origin code has been entered so as to allow the compiler   to process the new original code.   18 A computer system according to claim 16, ca-   characterized in that it includes means for re-initializing   be the compiler after modifying the criginre code, pro-   thus mentioning the compiler recompilation of the code original modified.   19 A computer system according to claim 16, ca-   characterized in that it comprises a terminal having a keyboard; and means which actuate the means of interruption in   response to keyboard operation.   20 A computer system according to claim 19,   characterized in that the editor includes means for   to inform the importance of the part of the original code treated by the compiler.   21 A computer system according to claim 20, ca-   characterized in that the publisher includes means for   request the re-initialization of the compiler in order to cause   the latter's recompilation of the original code.