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2-1 COBOL for the 21 st Century Nancy Stern Hofstra University Robert A. Stern Nassau Community College James P. Ley University of Wisconsin-Stout (Emeritus)

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Presentation on theme: "2-1 COBOL for the 21 st Century Nancy Stern Hofstra University Robert A. Stern Nassau Community College James P. Ley University of Wisconsin-Stout (Emeritus)"— Presentation transcript:

1 2-1 COBOL for the 21 st Century Nancy Stern Hofstra University Robert A. Stern Nassau Community College James P. Ley University of Wisconsin-Stout (Emeritus) John Wiley & Sons, Inc. 11th edition

2 2-2 The IDENTIFICATION and ENVIRONMENT DIVISIONs Chapter 2

3 2-3 Chapter Objectives To familiarize you with Basic structure of a COBOL program General coding and format rules IDENTIFICATION and ENVIRONMENT DIVISION entries

4 2-4 Chapter Contents Basic Structure of a COBOL Program Coding Requirements of IDENTIFICATION DIVISION Sections of ENVIRONMENT DIVISION Assigning Files to Devices in ENVIRONMENT DIVISION

5 2-5 Humor

6 2-6 Basic COBOL Program Structure Originally, each COBOL instruction coded on single line of 80 characters Positions on line reserved for special purposes Rules may differ for your compiler Rigid column rules dropped in 2008

7 2-7 Coding Rules Columns 1-6 and optional and rarely used today Column 7 for continuation, comment, starting new page Columns 8-72 for COBOL program statements

8 2-8 Coding Rules Column 7 * (asterisk) designates entire line as comment / (slash) forces page break when printing source listing - (dash) to indicate continuation of nonnumeric literal

9 2-9 Margin Rules Columns 8-72 divided into two areas –Area A - columns 8, 9, 10, 11 –Area B - columns Division, section and paragraph-names must all begin in Area A –First letter of name must begin in column 8, 9, 10 or 11 –Entry may extend into Area B

10 2-10 Margin Rules All other statements, clauses, and sentences begin anywhere in Area B (column 12, 13, 14, etc.) –Select entries in ENVIRONMENT DIVISION –Data description entries in DATA DIVISION –All PROCEDURE DIVISION instructions

11 2-11 Review of Margin Rules Division and Section Names –Begin in Area A, end with a period –Must appear on a line with no other entries Paragraph-names –Begin in Area A, end with period followed by space –May appear on line by themselves or with other entries

12 2-12 Review of Margin Rules Statements and Sentences –Begin in Area B –May appear on line by themselves or with other entries –Statements (e.g., OPEN, WRITE) may end with period but not recommended –Sentences (e.g., a paragraph made up of one or more statements) end with period followed by space

13 2-13 IDENTIFICATION DIVISION Provides identifying information about program Divided into paragraphs PROGRAM-ID only required paragraph Other paragraphs optional

14 2-14 IDENTIFICATION DIVISION Format IDENTIFICATION DIVISION. PROGRAM-ID. program-name. [AUTHOR. [comment-entry] …] [other optional paragraphs]

15 2-15 Understanding Instruction Formats Instruction formats describe syntax of all parts of COBOL language Describe required and optional elements, ordering and punctuation All formats in text are correct although additional options may be available

16 2-16 Rules for Instruction Formats Uppercase words are COBOL reserved words Lowercase words are user-defined entries IDENTIFICATION DIVISION. PROGRAM-ID. program-name. –DIVISION is reserved word –program-name is user-defined data-name Example

17 2-17 Rules for Instruction Formats Underlined words are required Punctuation if specified is required IDENTIFICATION DIVISION. PROGRAM-ID. program-name. –IDENTIFICATION, DIVISION required –PROGRAM-ID is required paragraph –Periods required after division header, paragraph name and program-name Example

18 2-18 Rules for Instruction Formats Brackets [ ] mean item is optional, braces { } mean one of enclosed items required Ellipses (...) mean entry may be repeated IDENTIFICATION DIVISION. PROGRAM-ID. program-name. [AUTHOR. [comment-entry] …] –AUTHOR paragraph optional –If included it may have any number of comment entries Example

19 2-19 ENVIRONMENT DIVISION Describes files and computer devices used to process them Required by programs that process files This division is machine-dependent since devices differ from computer to computer Only division that may change if program run on different computer

20 2-20 Sections of Environment Division CONFIGURATION SECTION –Describes computer used to compile/execute program –Optional and recommended that you omit it INPUT-OUTPUT SECTION –Describes input and output files and devices used by program –Required for all programs using files

21 2-21 INPUT-OUTPUT SECTION Follows CONFIGURATION SECTION (if coded) Includes FILE-CONTROL paragraph –Contains one SELECT statement for each file used by program –Each SELECT defines a file-name and assigns device name to that file

22 2-22 INPUT-OUTPUT SECTION Format INPUT-OUTPUT SECTION. FILE-CONTROL. SELECT file-name-1 ASSIGN TO implementor-name-1 [ORGANIZATION IS LINE SEQUENTIAL]. 1 1 Use this clause for all PC files so each line treated as separate record.

23 2-23 SELECT Statement file-names Choose meaningful file-names –EMPLOYEE-FILE instead of E-FILE –EMP-REPORT-FILE instead or OUT-FILE File-names are user-defined words –Words chosen by programmer to represent some element of program Must follow rules for forming user-define words

24 2-24 Rules for User-Defined Words 1.1 to 30 characters 2.Letters, digits, hyphens (-) only 3.No embedded blanks 4.At least one alphabetic character 5.May not begin or end with hyphen 6.May not be COBOL reserved word

25 2-25 SELECT implementor-names Conventions for these names vary widely among computers Most enable use of special device names for frequently used devices Printer SYSLST, SYS$OUT, PRINTER Disk DISC or DISK and disk file-name

26 2-26 SELECT implementor-names Special device-names example Select Transaction-File Assign to Disk "Data1". Select Report-File Assign to Printer. Some systems use name of file stored on disk (VAX or Alpha systems) Select Sales-File Assign to "Sales1".

27 2-27 SELECT Statements for PCs For PCs, use device names specifying –Drive on which file appears followed by a colon –Folder name if file is in a folder –Name of file PC example Select Inventory-File Assign To "C:\Inventory\Inv-File.dat".

28 2-28 ORGANIZATION clause for PCs This clause describes organization of records in the file Most PC disk files created as text files –Following data for each record, Enter key is pressed –Indicates end of the line and end of the record –If records 80 characters or less, each record appears on single line on screen or printer

29 2-29 ORGANIZATION clause for PCs Include LINE SEQUENTIAL to –Correctly read records from files when Enter key used to mark the end of each record –Create disk files with each record followed by Enter key so each record appears on separate line when printed

30 2-30 ORGANIZATION clause for PCs PC Example Select Sales-File Assign to "C:\Chapter2\Sales.dat" Organization is Line Sequential.

31 2-31 Coding Guidelines 1. Separate divisions by blank comment line, page eject symbol or blank line 2.Code a single statement per line 3.Code paragraph-names on line by themselves 4.Be liberal in use of comments. Box lengthy comments using asterisks.

32 2-32 Coding Guidelines 5. Code SELECT statements in logical order (input files first, then output files) although order not required 6. Use separate lines for SELECT, ASSIGN, ORGANIZATION clauses for readability 7.Avoid use of device-specific file- names

33 2-33 COBOL 2008 Changes Coding rules for Margins A and B will be recommended not required. PROGRAM-ID will be only paragraph in IDENTIFICATION DIVISION. All others can be specified as comments. Length of user-defined words will be increased from 30 to 60 characters.

34 2-34 Chapter Summary IDENTIFICATION DIVISION –Defines program name –Program name up to eight characters, letters and digits only, acceptable on all computers –PROGRAM-ID is only required paragraph, all others optional –Use comments by coding an * in column 7

35 2-35 Chapter Summary ENVIRONMENT DIVISION –Division is optional for COBOL 85 –Not needed for fully interactive programs –INPUT-OUTPUT SECTION required for any program using files –Only machine-dependent division since device specification, file-name rules vary among computers

36 2-36 Copyright © 2003 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages, caused by the use of these programs or from the use of the information contained herein.

37 2-37 The IDENTIFICATION and ENVIRONMENT DIVISIONs Chapter 2


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