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CobolNotes.md

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Overview

Notes on the COBOL programming languages as it applies to the MVS mainframe environment, with an emphasis on the older compiler versions as found on the Hercules with TK4- emulator environment.

References

Info on writing to a Data set

COBOL Compilers on the Hercules with TK3- emulator environment

  • CB545 V2 LVL78 01May1972 - COBUCG on the JCL EXEC - and s/360 pre COBOL 1974 Standard compiler

COBOL Program Structure

Page Column Layout

1 thru 6 7 8 thru 11 12 thru 72 73 thru 80
Seq #s C Area A Area B Comment

Column 7 is for a special purposes character

  • * - Marks the remainder of a line as a comment
  • / - Printing new line
  • - - Continuation of the prior line

DIVISIONS, SECTIONS, AND PARAGRAPHS start in Area A.

SENTENCE, STATEMENT, CLAUSE, WORD, CHARACTER start in Area B

SENTENCEs are made up of STATEMENTs and are terminated by period. A SENTENCE can have one STATEMENT or multiple STATEMENTs. The period is referred to as an implicit scope terminator. Prior to COBOL 75 (the Hercules 3.8 compiler i pre-COBOL 75) the period was used to terminate IF and PERFORM blocks, in addition to terminating statements. COBOL 75 introduced END-IF, END-PEFORM and END-EVALUATE explicit scope terminators.

Program Divisions

IDENTIFICATION DIVISION

Contains the PROGRAM-ID which is mandatory. It identifies the program name.

Also contains optional AUTHOR, DATE-WRITTEN, DATE-COMPILED, etc.

ENVIRONMENT DIVISION

  • CONFIGURATION SECTION

    • SOURCE-COMPUTER
    • OBJECT-COMPUTER

  • INPUT-OUTPUT SECTION

    • FILE-CONTROL

  • I-O SECTION

DATA DIVISION

  • FILE SECTION - Contains the file definitions
  • WORKING-STORAGE SECTION - Contains the programs variables
  • LINKAGE SECTION - used to link one program module to another

There a five basic data types in COBOL. They are defined using the PICTURE clause in the FILE and WORKING-STORAGE sections

  • S - Signed integers
  • 9 - Unsigned integers
  • V - Assumed Decimal, or . for an explicit decimal
  • A - Alphabetic character A-Z
  • X - Alphanumeric character A-Z, 0-9 and other characters

PICTURE Examples:

  • PIC -9(5) - a 5 digit signed integer.
  • PIC 9(10) - a 10 digit unsigned integer
  • PIC 9(6)V99 - an implied decimal with 6 digits to the left and 2 to the right. The actual decimal point isn't stored
  • PIC A(20) - can hold a 20 character alphabetic string.
  • PIC Z(20) - can hold a 20 character string with both letters, numbers, and special symbols, such as an email address.

For output (such as reports) you can specify other symbols as part of the PICTURE, such as $, +/-, ,

  • PIC -9(5) - proceed negative numbers with a minus sign.
  • PIC 9(6).99 - an explicit decimal is displayed/stored
  • PIC ZZZ,ZZ9 - display the commas in the number. The Z specifies that leading zeros should be suppressed.

Variables can be initialized using a VALUE clause

PROCEDURE DIVISION

Contains the program logic. There are no specific system define sections here as in the above division, but their can be user defined sections.