An overview of the 1974 COBOL standard
Contents
1. BY C FIRST DHbbHA S BY BBEFOREB AFTER INITIAL EN After executing the above INSPECT statement ID 1 would contain THESFEETBOFSTHEBDUCKBGOS OVERSTHESFENCEBBEFOREBTHESTAIL This example points out one of the limitations on the use of INSPECT the number of characters being replaced must equal the number of characters by which they are replaced Thus DE cannot be replaced by THES but the characters 5DE can be replaced by THES With the 1974 Standard the COBOL language has the features necessary for manipulation of character strings without each individual character string beginning in the leftmost character position of a data item The STRING statement allows a user to build a single data item from two or more data items The sending data items may be delimited by one or more character s or the entire sending item can be part of the receiving item A user can also indicate the relative starting position in the receiving item for the STRING operation The following example illustrates the use of the STRING statement DATA DIVISION Entries 01 WISH LIST 02 FILLER PIC X 4 VALUE GEEb 02 FILLER PIC X 33 VALUE SPACES 01 REL POSITION PIC 99 VALUE 5 01 STRING VALUES 02 FIELD1 PIC X 13 VALUE IbWISHBI BYOU 02 FIELD2 PIC X 24 VALUE WASKABFORTRANBPROGRAMMER PROCEDURE DIVISION Entries PARAGRAPH 1 STRING FIELD1 DELIMITED BY SPACES FIELD22. The DELETE verb logically removes a record from the file Once the statement has been executed the record cannot be accessed again The WRITE and REWRITE verbs insert and update respectively the records in the file Any file maintenance key associated with the file must be unique within all the records for the file The previous input output statement for the file must have been a READ statement The REWRITE statement causes the last record READ by the program to be logically replaced by the specified record The number of character positions in the record being rewritten and the record being replaced must be equal The WRITE statement causes a record to be inserted assuming the key does not already exist An important addition to the 1974 language specification for all I O modules is the FILE STATUS data item which contains information as to the success or failure of an I O operation The FILE STATUS clause located in the FILE CONTROL entry for a file specifies a two character alphanumeric data item and contains values which indicate the results of every statement which references that file explicitly or implicitly The operating system moves the values into the file status data item upon the completion of any statement which references the file The new I O modules provide the user greater flexibility and a wider range of functions than have been previously available The Indexed I O module in particular gives the user the ability to
3. then any referenced program names with the first six characters identical would be treated as referenc ing the same subprograms The action to be taken when there is not enough memory available for a called program can be specified in the ON OVERFLOW phrase of the CALL statement If this phrase is not specified the effects of the CALL statement are defined by the implementor THE INPUT OUTPUT MODULES The major enhancement of COBOL 74 over COBOL 68 is in the revision to the input output modules The From the collection of the Computer History Museum www computerhistory org 304 National Computer Conference 1975 aa Sequential I O module has been revised and the Random Access module has been replaced by two new ones Relative I O and Indexed I O with some degree of functional and syntactic similarity existing between the new Relative I O module and the old Random Access module Taken as a group the three I O modules provide the COBOL programmer with the file handling capabilities which are well beyond what has been possible previously Sequential I O The Sequential I O module for the 1974 Standard has all the features of the 1968 Standard with the exception of user defined labels and declarative label processing sec tions which are no longer supported by the COBOL language The data name option of the LABEL RECORDS clause and the USE statement option for label record processing were deleted A major new feature
4. extensive and the heart of the system the MCS is not well defined These considerations suggest a degree of skepticism vis a vis the degree of applicability of the Communication module Despite this skepticism it must be admitted that some capability is now available for message handling RECOMMENDATION COBOL 74 is in many ways a vast improvement over COBOL 68 New features have been added which contrib ute to the capability of the language the new I O modules enlarge its scope the Communication Module and enable the programmer to produce a better product the Inter program Communication and Debug modules Furthermore old modules have been enlarged and im proved We believe the efforts of the standardizing body ANSC X3jJ4 COBOL should now be directed toward producing a more complete and precise definition of the language The procedures of the American National Standards Institute require that action be taken to reaffirm review or withdraw the standard no later than five years following the publication of the current standard X3J4 should seriously consider a radical rewrite of the standard in an effort to make it more a standard and less a generalized user s manual A standard is supposed to be an authoritative measure by which correctness of other things may be determined condensed from Websters but it is a difficult task to measure correctness against a standard which is ambiguous and subject to inter
5. identifier A the results after the COPY takes place are ADD A TO B There can be more than one library available at compile time In this case the COPY sentence must contain the name of the library in which the text resides The presence of the REPLACING phrase in a COPY sentence causes the library text being copied to be edited prior to being inserted in the program There are several levels of editing that can be used Words literals identifiers and pseudo text can be replaced by like or different types of operators Pseudo text is bounded by pseudo text delimiters which are matching sets of double equal signs much like a nonnumeric literal which is delimited by sets of matching quotation marks The replacement of pseudo text is based on finding a matching set of character string s contained in the library text The replacement string may be longer or shorter than the characters replaced The following COPY statement illustrates the use of pseudo text to edit a library entry User s COBOL Library LIBRARY TEXT 01 IDI PIC X 54 VALUE IS bDEFEATSDEDUCTBDEFENSES DETAILS BBEBBE AHHH bE HHD Y COBOL Source Statement COPY LIBRARY TEXT REPLACING KDE BY THES AT BY ETBOFB CT BY CKSGOLOVERL SE BY CEBBEFOREL I From the collection of the Computer History Museum www computerhistory org The compiled results of a program with the above COPY statement are the sa
6. queue is empty then at the user s option the program can be forced to wait until a message becomes available or it can be directed to proceed immediately with execution of the next sequential statement During the RECEIVE operation all data items in the input CD record are updated by the MCS The SEND statement causes a message a message segment or a portion of a message or segment to be From the collection of the Computer History Museum www computerhistory org 306 National Computer Conference 1975 released to one or more output queues maintained by the MCS Prior to executing a SEND the user must specify in his output CD record area the number and names of the destinations to which the data is to be sent plus the length of the text in characters In the SEND statement itself the user specifies which transmission sentinel is to be used end of message end of group or end of segment When a SEND is executed the MCS must enqueue the data on the appropriate queue s and return the operation status to the CD for use by the program Line and page control may be exercised on line oriented devices A variation of the ACCEPT statement enables the user to determine the number of messages currently enqueued in any particular queue Prior to executing the ACCEPT statement the user must specify in his input CD the name of the queue or subqueue whose size is to be returned The MCS will return to the CD in the appropri ate p
7. An overview of the 1974 COBOL standard by MARGARET M COOK GEORGE N BAIRD WILLIAM M HOLMES PATRICK M HOYT L ARNOLD JOHNSON and PAUL OLIVER Department of the Navy Washington D C INTRODUCTION Since 1 July 1972 all COBOL compilers brought into the Federal Government have to be identified as implementing one of the levels of the Federal COBOL Standard The National Bureau of Standards which has the responsibility for the development and maintenance of Federal ADP Standards has delegated to the Department of Defense the responsibility for the operation of a Government wide COBOL Compiler Testing Service This responsibility is discharged by the Federal COBOL Compiler Testing Service FCCTS an activity of the Department of the Navy s Automatic Data Processing Equipment Selection Office Software Development Division through the imple mentation and maintenance of the COBOL Compiler Validation System CCVS a comprehensive set of com puter programs used to test COBOL compilers for compli ance with the Federal COBOL Standard In May 1974 the American National Standards Institute approved ANS Programming Language COBOL X3 23 19742 as the national standard for the COBOL language replacing USA Standard COBOL X3 23 1968 Federal Information Processing Standards Publication 21 1 adopts X3 23 1974 minus the Report Writer module as the Federal COBOL Standard As a result of these actions the Testing Service is engaged in th
8. DELIMITED BY SIZE INTO WISH LIST WITH POINTER REL PO SITION ON OVERFLOW GO TO PARAGRAPH 2 PARAGRAPH 2 After the execution of the STRING statement the data item WISH LIST l contains GEESIb WISHSIBWASKABFORTRANBPROGRAMMER The opposite is achieved by the UNSTRING statement which causes data in a sending field to be separated based on one or more delimiters and placed into multiple receiving fields A delimiter may be a single character or a combination of characters The SIGN clause allows a user to specify whether a separate character position is used for the sign in numeric items and to indicate whether the position of the sign is leading or trailing The PROGRAM COLLATING SEQUENCE clause per mits one to specify ASCII or some other collating sequence However changing the collating sequence for a program will necessarily require consideration of all state ments which depend upon a character s relative position in a given collating sequence for example the SEARCH statement the SORT MERGE statement or alphanumeric comparisons in an IF statement Library Several major changes have been made to the Library module There are now no restrictions on where a COPY statement may appear in a COBOL program A COPY sentence may appear anywhere that a COBOL word may appear As a result rather strange looking source code can be produced e g ADD COPY XX TO B If the content of the library text XX contains the single
9. IAL clause When the ACCESS MODE IS DYNAMIC is specified records may be processed either randomly or sequentially through use of the appropriate I O statement The access mode for a file need not be the same as the mode in which the file was created When accessing the file sequentially the records are retrieved in ascending order based on the key contents The START statement provides positioning within an indexed or relative file for subsequent sequential retrieval of records When processing the file randomly From the collection of the Computer History Museum www computerhistory org records are stored or retrieved based on the data contents of the record key Records are accessed based on the current key of reference The key of reference prime record key or alternate record key is established at the COBOL instruction level The default key of reference is the prime record key but an alternate key of reference may be specified in a random READ statement Any subsequent sequential read uses the key of reference established by the last random read or START statement File maintenance The means of maintaining mass storage files i e record insertion record deletion and record updating is accom plished through the use of the verbs DELETE WRITE and REWRITE Only the prime record key associated with the file is used in providing all file maintenance func tions i e RELATIVE KEY for Relative I O and RE CORD KEY for Indexed I O
10. arameter fields the message count and the status of the operation Only input queues may be measured in this way The ENABLE and DISABLE statements direct the MCS to allow and inhibit respectively data transfer between specified output queues and destinations for output or between specified sources and input queues for input The queues or destinations involved must be named in the appropriate CD before execution of the statement These statements make and break the logical connections be tween the queues managed by the MCS and the network of communication devices but they do not affect the logical connections between the various queues and the program itself The specification of a key or system password is required in both statements in order to prevent indiscriminate use of the facility by a COBOL user who is not aware of the total network environment and who may therefore disrupt system functions by the un timely issuance of ENABLE and DISABLE statements A special option permits the user to specify the symbolic name of a specific device in his input CD and then request enabling or disabling of the logical paths between that device and all queues and subqueues linked to it Finally there is the added capability to designate in a COBOL communication program that it is to be scheduled for execution automatically by the MCS whenever the MCS determines that there is message processing to be done This is accomplished by spe
11. cifying an option in one input CD in the program Subsequently when the MCS invokes the program it will place the name of the queue or subqueue which prompted the action in the appropriate parameter fields of the input CD There are means to test within the program whether the program was invoked by the MCS or scheduled through job control language Inadequacies The basic problem with the Communication module as it now stands is the fact that the MCS and its interface to the network of peripheral devices is so ill defined Al though the concept of the MCS is never formally intro duced except in Appendix C of the Standard its existence is implied throughout the specification for the Communica tion module by frequent references to it the MCS by name Unfortunately the appendices are not considered a part of the formal COBOL language specification and thus they are in no way binding At best the appendix can be considered a suggested guideline for implementation In other words it can only serve to enlighten the reader as to what the Programming Language Committee PLC of the Conference on Data Systems Language CODASYL might have had in mind when they designed the specification for the Communication module Contributions It is not really possible to assess the usefulness of the new Communication module Such an assessment must await the use of the features in a communication environ ment The features themselves are not
12. ction and we ignore the Report Writer as being beyond the scope of the Federal Standard Section 2 3 of Appendix B of the X3 23 1974 Standard documents in greater detail the modifications made to the 1968 Standard and the additional language features added for the 1974 Standard Nucleus Three new verbs have been added to the Procedure Division of the Nucleus module INSPECT STRING and UNSTRING The INSPECT verb replaces the old EXAM INE verb and provides expanded editing capabilities With an INSPECT statement one can count and replace occurrences of either single characters or groups of characters in a data item For each of these INSPECT functions the BEFORE or AFTER phrase allows one to specify that the function begins or ends upon encountering a given character or group of characters As an example of the INSPECT statement consider the following source code Coding examples in this paper will contain formatting errors due to the typesetting require ments DATA DIVISION entries ID 1 PIC X 54 VALUE KDEFEA TBA BK DEDUCTBBH BEAK HHHS DEFENSEBABB EASABDETAIL PROCEDURE DIVISION entries INSPECT ID 1 REPLACING ALL BDE by THES FIRST A BY E FIRST VBB BY OFS FIRST T BY K AFTER INITIAL UC FIRST HbbEHHH E BY bGOLOVERD From the collection of the Computer History Museum www computerhistory org 302 National Computer Conference 1975 FIRST S
13. e Computer History Museum www computerhistory org
14. e development of a new COBOL Compiler Validation System incorporating tests for the revised language This paper presents an overview of COBOL 74 highlighting the new features in the language major language deficiencies and important contributions to the programming discipline All comments made with regard to COBOL 68 or COBOL 74 will be based on the language as defined in References 3 and 2 respectively REVISIONS TO THE COBOL 68 MODULES The Nucleus Sequential I O and Library modules of COBOL 68 have undergone major revisions The Table Handling and Segmentation modules are essentially the same modules as appeared in the 1968 COBOL Standard The Random Access module has been replaced by the new modules Relative I O and Indexed I O and the specifica tions for the Report Writer module have been rewritten 301 ol The Sort module has been expanded into the Sort Merge module by the addition of the MERGE verb The Table Handling module in COBOL 74 consists of two levels instead of the previous three levels and the punctuation changes in the 74 Standard have relaxed the rigid rules for the use of parentheses and commas in referencing table items Literals and index names may be mixed when referencing a table item and an index may be incremented or decremented by a negative value In the remainder of this section we concentrate on the new features of the Nucleus and Library modules The I O modules will be covered in a later se
15. ere is not enough object time memory can be specified and the memory areas occupied by called programs can be released and made available to the operating system Features The CALL statement causes control to be transferred from one object program to another object program in the same run unit If the subprogram name is known at compile time the CALL statement operand is a nonnu meric literal The subprogram name can also be specified dynamically as the contents of a data name The data items which are shared with the called program are specified in the USING phrase of the CALL statement In the subprogram the shared items are specified in the USING phrase of the PROCEDURE DIVISION header and defined as data descriptions in the LINKAGE SECTION There must be a one to one corre spondence between the operands in the CALL statement An Overview of the 1974 COBOL Standard 303 and the operands in the PROCEDURE DIVISION header of the called program The data descriptions for corre sponding operands must define an equal number of character positions but the data descriptions do not have to be identical No space is allocated in the called program for items defined in the LINKAGE SECTION and refer ences to items in the LINKAGE SECTION are resolved at object time The CALL statement also permits the user to specify the action to be taken when there is not enough memory available for a subprogram This is done in the imperative state
16. fies the size of the top and bottom margins for a logical page the number of lines comprising the page body and the line number within the page body where the footing area begins The values given in the LINAGE clause may be specified as integer constants or the contents of data names If the values are integer constants each page has the same format through out execution of the programs If the values are the contents of data names the values at the time the file is opened specify the first logical page Each time a new page is started the values of the data items are examined to determine the values for the current page Thus the logical format and size of a page can be changed for each new page in a file designated for printer output New Input Output Modules The INDEXED I O and RELATIVE I O are new modules in the 1974 Standard Because the Indexed I O module is the most complex and important of the two we will concentrate our remarks on it mentioning important features of the Relative I O module where appropriate Features The INDEXED I O and RELATIVE I O modules pro vide the capabilities for accessing a file in a predefined mode INDEXED I O also provides the capability of defining several paths of information retrieval In a Relative file records may be stored randomly but are identified by a relative record number on which record storage and retrieval is based The record number or key must be unique and is t
17. he only means by which the file may be accessed The record storage relationship for an Indexed file however is based upon one or more indexes associated with the file Thus an Indexed file may be accessed through one or more record keys The prime and alternate keys are defined within the SELECT clause of the FILE CONTROL paragraph for Indexed files The contents of the prime key must be unique for each record in the file This is the base key from which the file is constructed and is used for inserting updating and deleting records The user may specify one or more alternate keys for the file Unlike the prime record key alternate keys may be non unique The content of the keys which are used to retrieve records are considerably more flexible in the Indexed I O module than in the Relative I O module Under the Relative I O file organization the record reference key must be an unsigned integer and is defined outside the record description entries for the file In the Indexed I O organization the record reference key must be an alphanu meric data item which can contain any combination of characters in the computer s character set and must be defined within a record description entry for the file The language specification for COBOL 74 allows for sequential random or dynamic access within both Relative I O and Indexed I O modules The access mode for a given file is indicated by use of the ACCESS MODE IS RANDOM or ACCESS MODE IS SEQUENT
18. implement multi key retrieval functions and provide a closer relationship of the capabilities of data base management systems entirely within the scope of the COBOL Language THE COMMUNICATION MODULE The motivating factor behind including a Communica tion Module in COBOL 1974 was the advent within the past decade of computer systems using remote terminals and the use of these terminals for message processing An Overview of the 1974 COBOL Standard 305 applications Heretofore the COBOL user has been un able to perform this class of interactive operations without resorting to system dependent facilities such as assembly language support routines Many implementations of COBOL permitted limited degree of access to remote terminals via the ACCEPT and DISPLAY verbs but obviously these posed serious limitations on capabilities by limiting transmission to an on demand basis and in no case could a program be notified of unsolicited input from a terminal The Communication module in COBOL 1974 attempts to solve these deficiencies by providing four new I O verbs RECEIVE SEND ENABLE DISABLE and interfacing COBOL programs to any configuration of remote terminals via a set of message queues The operation of the message queues and the remote terminals is handled by a Message Control System MCS a black box software package which is largely implementor defined and by its very nature is system dependent The MCS must
19. in the 1974 Standard allows a user to process character code sets other than the system s native character code set on input and output operations The CODE SET clause of the File Description entry specifies the character code set which is used to represent the data on the external media When this clause is included in a File Description entry characters are converted to the native character set on input or converted from the native set to the code specified on output The CODE SET clause can only be used in File Descriptions which are not mass storage files and the external code representations are limited to the ASCII code set the native character code set or other character code sets supported by the implementation The Sequential I O module provides the capability to add records to the end of an existing sequential file Execution of an OPEN EXTEND statement positions a file immediately following the last logical record of the file Subsequent WRITE statements for that file add records to the end of the file as if the file had been opened in the OUTPUT mode The FILE STATUS clause of the File Control entry and the REWRITE statement are also elements of the Relative I O and Indexed I O modules and these two new features are discussed later In the Sequential I O module for the 1974 Standard one can describe the logical page format for a printer destined file through the LINAGE clause in the File Description entry The LINAGE clause speci
20. me as a program in which the following source code appeared 01 ID1 PIC X 54 VALUE IS THEBFEETBbOFSTHESDUCKSGOLOVERS THESFENCEBBEFORESTHESTAIL THE DEBUG MODULE In the 1968 Standard there were no explicit proce dures for specifying what debugging actions if any would take place during the execution of a COBOL program The DEBUG module for the 1974 Standard includes language elements which are designed for debugging COBOL pro grams Their inclusion in the COBOL language permits a user to consider the debugging of source programs in the design of an application not as an afterthought when problems are encountered The USE FOR DEBUGGING statement identifies the user items that can be monitored by the associated debugging section The debugging algorithm which is defined in the debugging section can be controlled by both a compile time switch and an execution time switch Debug lines are source statements whose inclusion or omission from an object program is controlled by a compile time switch There is a special register called DEBUG ITEM which can be accessed in debugging sections This special register contains information relative to the source code which causes the execution of a debugging section INTER PROGRAM COMMUNICATION The Inter Program Communication module provides a means for a program to transfer control to one or more subprograms and the sharing of data among these pro grams The action which is taken when th
21. ment of the ON OVERFLOW phrase of the CALL statement The CANCEL statement releases the memory area occupied by the program referred to in the CANCEL statement A CALL to a program that has been cancelled causes that program to be loaded and executed in its initial state The EXIT PROGRAM statement marks the logical end of a called program Control is returned to the calling program when this statement is executed More than one EXIT PROGRAM can appear in a subprogram but the EXIT PROGRAM statement must be the only sentence in a paragraph Inadequacies The INTER PROGRAM COMMUNICATION module restricts the possible operands which may appear in the USING phrases The operands must refer to 77 or 01 level number items and may not be defined in the REPORT SECTION of the calling program There are implementor defined areas in the Inter Program Communication module which could cause prob lems in program portability between systems The relation ship between the operand in the CALL CANCEL state ment and the referenced program is implementor defined This means that even though the program name is a user defined word and thus could be 30 characters the implementor may limit the actual number of characters which are used to establish linkage between the called and calling programs If a user has subprograms on a system which recognizes the first 10 characters of the program name and moves to an implementation which recognizes the first six
22. pretation Both the syntax and semantics of the language should be expressed as formal grammars and defined in an appropriate meta language The efforts of ANSC X3J1 to so define the PL 1 From the collection of the Computer History Museum www computerhistory org An Overview of the 1974 COBOL Standard 307 language is an admirable example of what can be done REFERENCES When a language is well defined there can be no j ambiguities and no doubt as to what is valid and what is i Baird N The DOD Compiler Validation Sreem Proe 1073 not There is seldom a need for interpretation Such FJCC AFIPS Press Volume 41 pp 819 827 definitions are also of significant value when a compiler 2 American National Standard Programming Language COBOL X3 23 implementor chooses to use a syntax directed or other 1974 American National Standards Institute Incorporated New York 1974 automated parsing technique Finally a precise definition Set l woud make mich simpler the task of determining the 3 American National Standard COBOL X3 23 1968 American Na tional Standard Institute Incorporated New York 1968 degree 0 which COBOL compilers conform in their 4 Federal Information Processing Standards Publication 21 1 U S translation of COBOL programs to the Standard Government Printing Office Washington D C pending From the collection of the Computer History Museum www computerhistory org From the collection of th
23. provide the logical interface between the COBOL communication object program and the systems network of communication devices by performing line discipline including such tasks as dial up polling and synchronization and by performing device dependent tasks such as character translation and insertion of control characters The COBOL programs interface with the MCS through the programs Communi cation Descriptions or CD s CD s are placed in the Communication Section which follows the File Working Storage and Linkage Sections in the Data Division The CD establishes either an input or an output path for messages and provides parameter fields for passing information between the program and the MCS Features For the Procedure Division the Communication Module introduces four new verbs RECEIVE SEND ENABLE and DISABLE plus a new variation for an old one ACCEPT The following paragraphs summarize these statements as presented in the formal language specifica tion for the Communication module The RECEIVE statement makes available to the COBOL program a message message segment or a portion of a message or segment Prior to executing a RECEIVE the user must specify in his input CD record area the name of the queue or subqueue he wishes to address Executing the RECEIVE then effects dequeuing of a message from the appropriate queue and placing of that message into the field designated by the user If the addressed
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