COBOL-SO: The new structured language

Transcription

1 COBOL-SO: The new structured language by JEROME GARFUNKEL Jerome Garfunkel Associates, Inc. Litchfield, Connecticut ABSTRACT This paper includes a presentation of the most important new features of COBOL- 80, with examples for each. In addition, an analysis of the potential costs and benefits of this new language is presented. Finally, criticism of potential incompatibilities is discussed by Jerome Garfunkel. Previously published in Data Management Magazine, October

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3 COBOL-80: The New Structured Language 219 The features discussed in this paper are among the more significant new features of the draft proposed revised X3.23 American National Standard Programming Language COBOL (COBOL-80). The features presented here represent only a sample of all the new features of the revised COBOL standard. Many other more subtle features of COBOL-80 are included as well. Based on my own analysis as well as on a government analysis conducted on a sizable sample of its own program inventory, I expect a significant increase in productivity will be derived from using COBOL-80 in program development and maintenance. Particularly in the area of program maintenance, although the cost savings will be deferred as programs go through their normal life cycle, the productivity gains derived from the maintenance of well-structured COBOL-80 programs will be a significant factor in systems maintenance operating costs. This revision of the COBOL standard has, in addition to the new features, numerous clarifications of poorly defined (ambiguous and undefined) rules that existed in the previous COBOL-74 and COBOL-68 standards. These clarifications, although constructively serving the COBOL user community at large, may inadvertently conflict with a specific implementor's COBOL compiler. This occurs when a specific implementor-defined interpretation of an ambiguous rule occasionally differs from the newly defined standard interpretation. Much attention has been paid to this group of features over the past few years. Many of the new features of COBOL-80 will greatly ease the use of COBOL in structured programming environments. Some of the new features specifically useful in structured programs are included in the following sections. EVALUATE The EVALUATE verb provides a means of testing multiple conditions and specifying multiple control branches (s'ee Figure 1). PERFORM An in-line version of the PERFORM statement is now permitted. In addition "DO-while" and "DO-until" constructs can now be written with the addition of the WITH TEST BEFORE and WITH TEST AFTER clauses. PERFORM WITH TEST AFTER UNTIL X > = 100 ADD 1 TOX MOVE TABLE-ITEM (X) TO TABLE-ITEM ( X + 1) END-PERFORM Note the new relational operator GREATER THAN OR EQUAL, and the new relative subscript (X + 1). STRUCTURED CONDITIONAL STATEMENTS With the inclusion of 19 scope terminators (i.e., END-IF, END-READ, END-ADD, etc.), constructs of nested conditional statements may be written with clarity. IF FINAL-RECORD-PROCESSED THEN PERFORM LAST-TRANSACTIONAL-PROC. READ BATCH-KEY-FILE AT END EXIT PROGRAM END-READ IF BATCH-KEY = "D" THEN PERFORM DELETION-PROC. ELSE PERFORM MODIFY-PROCEDURE END-IF ELSE PERFORM NORMAL-RECORD-PROCEDURE CONTINUE END-IF EVALUATE AGE-OF-DEBT ALSO WHEN OTHRU30 ALSO WHEN OTHRU 30 ALSO WHEN 31 THRU 60 ALSO WHEN 31 THRU 60 ALSO WHEN 31 THRU 60 ALSO WHEN 61 THRU 90 ALSO WHEN 61 THRU 90 ALSO WHEN 61 THRU 90 ALSO WHEN 91 THRU 999 ALSO WHEN 91 THRU 999 ALSO END-EVALUATE CREDIT-RATING "A" THRU "B" "e" "A" "B" "e" "A" "B" "e" "A" "B"THRU"C" PERFORM NO-NOTICE PERFORM MILD-NOTICE PERFORM MILD-NOTICE PERFORM NORMAL-NOTICE PERFORM FIRM-NOTICE PERFORM NORMAL-NOTICE PERFORM FIRM-NOTICE PERFORM COLLECTIONS PERFORM FIRM-NOTICE PERFORM COLLECTIONS Figure I-The EVALUATE Statement

4 220 National Computer Conference, 1984 FALSE CONDITION BRANCH To add structured symmetry to all conditional clauses (AT END, ON SIZE ERROR, etc.) a negative version of the clause is also allowed as in: READ AT END NOT AT END END-READ NESTED PROGRAMS MASTER-FILE EXIT PROGRAM PERFORM PROCESS-RECORD Complete programs may be wholly contained within other programs. This permits, among other things, the outside program to specify GLOBAL data items, which may be shared by any of the contained (inside) programs; as in this example: 01 SHARED-DATA IS GLOBAL X(20). Additionally, GLOBAL USE procedures may be specified in the DECLARATIVE section of the outer program that allows for file error processing in the contained programs to be centralized and controlled by the outer (Master) program: USE GLOBAL AFTER STANDARD ERROR PROCEDURE ON INPUT. CALL Data items that are passed to "sub-programs" may protect their contents from being modified by the addition of the BY CONTENT phrase of the CALL statement. CALL PAYROLL USING BY CONTENT WEEKLY-PAY, YTD-PAY. SYMBOLIC CHARACTERS The symbolic character clause in the SPECIAL-NAMES paragraphs provides a means for a programmer to specify a user-defined name for nonprintable characters in the ASCII (or other) character sets. SYMBOLIC CHARACTER BELL IS 8 IN ASCII In this example 8 refers to the eighth ordered character in the ASCII character set, and BELL is a user-defined figurative constant. FILLER The word FILLER is optional and is no longer restricted to elementary data items DE-EDmNG COUNTER-1 COUNTER-2 999V99. X. 999V99. Numeric-edited data items ( $$$,$$$) may be moved to a purely numeric data item ( 9(6)V99). This results, for example, in moving a data item that contains $1,234 to a data item containing SORT Multiple output files are permitted. In addition, the WITH DUPLICATES IN ORDER clause now allows the programmer to specify that duplicate sort keys appearing on the input file will be in the same sequence on the output file. INITIALIZING SUB-PROGRAMS When the PROGRAM-ID of a subprogram contains the phrase IS INITIAL after its program name, the programmer can be assured that all data values will be initialized before it starts executing. SORT ON ASCENDING KEY WITH DUPLICATES IN INPUT PROCEDURE IS GIVING SORT-WORK FILE WORK-ORDER-NUMBER ORDER ED IT-INPUT-PROCESS DAILY-WORK-SEQ DAILY-WORK-REL DAILY-WORK-INDX. PROGRAM-ID. ACCOUNTS-PAYABLE IS INITIAL. OCCURS-VALUES AND SUBSCRIPTS Seven dimensions (seven levels of subscripting) may now be specified (previously only three levels were provided). Also, initial values may now be specified for table elements without the need to REDEFINE the table TABLE-ELEMENT 999V99 OCCURS 100 TIMES VALUE ZERO. Note also that the SORT input procedure (EDIT-INPUT PROCESS) may reference procedures outside of the SORT section. Likewise, procedures within the SORT may be referenced by procedures in the main program. REFERENCE MODIFICATION Programmers may now reference a portion of a data item without needing to REDEFINE that portion previously in the DATA DIVISION, MOVE TELEPHONE (4:3) TO EXCHANGE

5 COBOL-80: The New Structured Language 221 In the above example only the fourth, fifth, and sixth position of the data item TELEPHONE are moved (starting in position 4: for a length of 3). I suggest that programmers be careful when using this feature because its misuse can lead to poorly documented programs. INITIALIZE A series of subordinate elementary data items may be initialized all at once using the INITIALIZE verb. Given the following group data item: 01 SCREEN-PAGE. 03 NAME 03 TELEPHONE 03 BALANCE-DUE 03 CUST-STATUS X(20). 999B999B V99. A. if a programmer writes INITIALIZE SCREEN-PAGE, all numeric data items will be cleared to zero and all nonnumeric data items will be cleared to spaces. There are facilities to restrict the initializing process to certain classes of data (numeric only, alphanumeric-edited only, etc.) as well as to initialize fields to values other than zero and spaces. INSPECT... CONVERTING The CONVERTING clause of the INSPECT statement permits a shorthand way of writing multiple character replacement clauses. 01 BOTTLE X(5) VALUE "WATER". INSPECT BOTTLE CONVERTING "ATR" TO "IN" This INSPECT statement results in three character replacements ("A" to "I", "T" to "N", and "R" to space). It is a cheap way to PERFORM miracles in COBOL-80 by converting WATER to WINE. REPLACE To aid the programmer in dealing with possible conflicts in new reserved words with COBOL-74/68 pro~ams, the RE- PLACE statement operates on source text and converts the source program before it is compiled. REPLACE = = END-READ = = BY ==END-READ-PROCEDURE== = = CLASS = = BY ==DATA-CLASS== ==ALPHABETIC== BY = = ALPHABETIC-UPPER = =. I expect that this will be most useful where COBOL installations create standard conversion library routines that can be copied into individual programs. RECORD DELIMITER A means of specifying Variable Length Record conventions is provided in the FILE-CONTROL paragraph. SELECT ASSIGN TO ORGANIZATION IS RECORD DELIMITER IS DAY-OF-WEEK INDEXED-FILE A DISC INDEXED STANDARD-I. This reserved word DAY-OF-WEEK represents a one digit character: 1 = Monday, 2 = Tuesday, 3 = Wednesday, etc. It is used as follows: CLASS ACCEPT DAY-CODE FROM DAY-OF-WEEK A new CLASS clause in the SPECIAL-NAMES paragraph allows a programmer to name his own class of characters. CLASS FIRST-HALF-ALPHA-UPPER IS "A" THRU "M" These new features, along with some other more subtle additions and changes, contribute to an up-to-date application language complementing current trends in structured programming methodologies. * * Those with questions regarding the revised COBOL 80 standard are invited to contact the author at Jerome Garfunkel Associates, Inc., Cobble Court, Litchfield, Connecticut

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