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COBOL - Structured Programming

COBOL - Introduction. A program - is a set of instructions that enable a computer to process data. There are two types of programsOperating System programsApplication programsOperating Systems:All programs run under the control of an operating systemThis program monitors and control the overall operation of the computerApplication programsTakes input data and converts it to meaningful output information.

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COBOL - Structured Programming

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    1. COBOL - Structured Programming Structured programming use logical control structures to specify the order in which instructions are executed. These structures are the same for all languages The four logical structures are Sequence Selection Iteration Case structure

    3. COBOL - History COBOL is an acronym that stands for Common Business Oriented Language. COBOL was developed in the 1950s; and was designed for applications with large volumes of Data To date over 50% of computer code in existence is in COBOL

    4. COBOL - History COBOL’s popularity is due largely to the USA’s Department of Defense which played in leading role in standardizing the COBOL language

    5. Read and understand program specifications Draw hierarchy charts Draw program flowcharts Write program code Compile a program and correct errors Test-run the program with test data Document the program Steps in program Development- COBOL programming context

    6. There are four main divisions in a COBOL program IDENTIFICATION DIVISION ENVIRONMENT DIVISION DATA DIVISION PROCEDURE DIVISION Divisions and Programming Area

    7. The divisions are coded in a text Editor. The divisions are coded in that particular order Name of the division and actual word ‘DIVISION’ are coded separated by a single space Each division plays a specific role in the COBOL program Notes to remember about Divisions

    8. columns 1-6 Optional sequence number column 7 Comment line (with an *) (ignored by compiler) columns 8-11 Area A (division heads, paragraphs, FD, 01entries) columns 12-72 Area B (All other entries) columns 73-80 Program identification(also ignored by the compiler) Rules for the Coding a COBOL program

    9. Identifies the program Example 1.0 IDENTIFICATION DIVISION

    10. There are two sections in this division Configuration section (Hardware details; this section is NOT NEEDED) Input-Output section(File details) 2.0 ENVIRONMENT DIVISION

    11. This DIVISION typically contains two sections FILE SECTION, and WORKING-STORAGE SECTION File section deals with Input and Output file descriptions FD- File description (starts in Area A) 01 - to describe the record layout (also in area A) Working Storage section Is the section where the input and output records are manipulated and all other variables needed are defined. Typically contains the variables, heading lines and detail record 3.0 DATA DIVISION

    12. In a COBOL program, you’ll find the following words Words Reserved words User Defined words Constants or Literals Non-Numeric Numeric Figurative constants Note: Reserve words, and User Defined words are case NON-sensitive COBOL Language Elements

    13. Reserved words See Appendix B, page 700 User Defined words (page 85) These are data names for storage, paragraph, and section names Examples: EMPLOYEE-NAME-OUT WS-END-OF-FILE-INDICATOR Rules: max 30 characters A-Z, 0-9, and hyphen (-) must start and end with A-Z, or 0-9 (paragraph ad section name are the only user defined words that are allowed to start with 0-9) cannot begin or end with hyphen must be at least one alphabetic character cannot be a reserved word COBOL Language Elements

    14. Non-Numeric Literals these are string constants Examples: “Summary of Loans Report” “ABC” Rules: max 160 characters quotation marks are required before and after (single or double - compiler option) contents between the quotes are case-sensitive COBOL Language Elements

    15. Numeric Literals these are hard-coded numbers Examples: 12.45 -1 Rules: max 18 digits +, - must appear on the left of the number COBOL Language Elements

    16. X Alpha-numeric (1 byte) 9 Numeric (1 bytes) S Operational SIGN (does not take up any space) e.g. 05 WS-CREDIT PIC S9(3) V Implied Decimal Point e.g. 05 WS-SALARY PIC 9(5)V9(02) Non-Edited Picture Characters

    17. Data File of SALEFILE 111111111MOOING MARTY 001451255000 222222222PATSY POTATO 450003569050 333333333ROWDY RODENT 205001259020 444444444STARING STACEY 000090000650 The File Description: FD SALES-FILE RECORD CONTAINS 80 CHARACTERS DATA RECORD IS SALES-REC. 01 SALES-REC. 05 EMPLOYEE-NUM-IN PIC 9(09). 05 NAME-IN PIC X(20). 05 QUANTITY-IN PIC 9(05). 05 AMOUNT-IN PIC 9(05)V99. 05 FILLER PIC X(39) Note the use of X and 9 and numbers in parentheses Example Input file and File Description

    18. Main Memory Example Input file and File Description

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