chapter 2 cobol language fundamentals

Structured COBOL Programming, Stern & Stern, 9th Edition

CHAPTER 2Cobol Language Fundamentals

BASIC STRUCTURE OF A COBOL PROGRAM

CODING RULES• A COBOL statement is subdivided into

72 positions or columns.

• Column 7 of a COBOL program has three primary purposes:

1. By coding an * (asterisk) in column 7, an entire line can be designated as a comment.

2. It can be used to force the printing of subsequent instructions on the next page of the source listing.

3. It can be used for the continuation of nonnumeric literals.

DEBUGGING TIP

• Use uppercase letters for instructions;– use lowercase letters for

comments.

• Page-Eject with a Slash (/) in Column 7 can also be used to skip to the next page when the source listing is being printed.

CODING RULES: Areas A and B• Positions 8--72 of a standard COBOL

program contain program statements:

– Column 8 is labeled the A area

– Column 12 is labeled the B area

• Entries in Area A, may begin in position 8, 9, 10, or 11.

– Most often, Area A entries begin in position 8.

• If an entry is to be coded in Area B, it may begin anywhere after position 11.

TYPES OF COBOL ENTRIESDivisions, sections, and paragraphs

begin in Area A. Examples include:

• DIVISIONSIDENTIFICATION DIVISION.ENVIRONMENT DIVISION.DATA DIVISION.PROCEDURE DIVISION.

• SECTIONSFILE SECTION.WORKING-STORAGE SECTION.

TYPES OF COBOL ENTRIES Divisions, sections, and paragraphs begin

in Area A. Examples include:

• PARAGRAPHS

PROGRAM-ID.

0-MAIN-MODULE.

1-BUILD-DETAIL-LINE.

• Statements and sentences begin in Area B; for example:

SELECT PAYROLL ASSIGN TO DISK.

ADD AMT-IN TO TOTAL.

TYPES OF COBOL ENTRIES

•MARGIN RULES

1. Division, section, and paragraph-names begin in Area A.

2. All other statements, clauses, and sentences begin in Area B.

CODING REQUIREMENTS OF THE IDENTIFICATION DIVISION

Paragraphs in the IDENTIFICATION DIVISION

IDENTIFICATION DIVISION.

PROGRAM-ID. program-name.

[AUTHOR. [comment-entry] . . .]

[INSTALLATION. [comment-entry] . . .]

[DATE-WRITTEN. [comment-entry] . . .]

[DATE-COMPILED. [comment-entry] . . .]

[SECURITY. [comment-entry] . . .]

Rules for Interpreting Instruction Formats

1. Uppercase words are COBOL reserved words

2. Underlined words are required.

3. Lowercase words represent user-defined entries.

4. Braces { } denote that one of the enclosed items is required.

Rules for Interpreting Instruction Formats

5. Brackets [ ] mean the clause or paragraph is optional.

6. If punctuation is specified in the format, it is required.

7. Dots … or ellipses (…) means additional entries of the same type may be optionally added.

COBOL 2000+ CHANGES

•All paragraphs AUTHOR through SECURITY have been deleted from the COBOL 2000+ standard since they can be easily replaced with comments.

QUESTIONS?

SELF-TEST

1. If an entry must begin in Area A, it may begin in position _____ ;

if an entry must begin in Area B, it may begin in position _____ .

Solution: 8, 9, 10, or 11; 12, 13, 14, and so on

SELF-TEST

2. The four divisions of a COBOL program must appear in order as _____ ; _____ ; _____ ; and, _____ .

Solution: IDENTIFICATION;

ENVIRONMENT;

PROCEDURE

SELF-TEST

3. What entries must be coded beginning in Area A?

Solution: Division, section, and paragraph-names

SELF-TEST

4. Most entries such as PROCEDURE DIVISION instructions are coded in Area _____ .

Solution: B

SELF-TEST

5. _____ and _____ must each appear on a separate line. All other entries may have several statements on the same line.

Solution: Division names; section names

SELF-TEST

6. The first two entries of a COBOL program must always be _____ and _____ .

Solution: IDENTIFICATION DIVISION. PROGRAM-ID. program-name.

SELF-TEST

7. Each of the preceding entries must be followed by a _____ , which, in turn, must be followed by a ____ .

Solution: period; space or blank

SELF-TEST

9. Code the IDENTIFICATION DIVISION for a program called EXPENSES for a corporation, Dynamic Data Devices, Inc., written January 18, 2007. This program has a security classification and is available to authorized personnel only. It produces a weekly listing by department of all operating expenses.

SELF-TEST9. Suggested solution:

IDENTIFICATION DIVISION.

PROGRAM-ID. EXPENSES.

*AUTHOR. N. B. STERN. *INSTALLATION. DYNAMIC DATA DEVICES, INC.

*DATE-WRITTEN. 1/18/2007.

*DATE-COMPILED. 1/18/2007.

*SECURITY. AUTHORIZED PERSONNEL ONLY.

THE SECTIONS OF THE ENVIRONMENT DIVISION

• The ENVIRONMENT DIVISION is the only machine-dependent division of a COBOL program.

• Entries in this division will depend upon:– (1) the computer system and

– (2) the specific devices or hardware used in the program.*

*Interactive programs that use keyed data as input and display screen output will not need this division.

THE CONFIGURATION SECTION– Supplies information about the computer

on which the COBOL program will be compiled and executed.

SOURCE-COMPUTER: – The computer that will be used for

compiling the program.

OBJECT-COMPUTER: - The computer that will be used for

executing or running the program.* SOURCE- COMPUTER and OBJECT-

COMPUTER are coded primarily as documentation entries.

The CONFIGURATION SECTION

• All section names, like division names, are coded in Area A.

• The CONFIGURATION SECTION, if coded, will follow the ENVIRONMENT DIVISION entry in Area A.

• SOURCE-COMPUTER and OBJECT- COMPUTER, as paragraph-names, would also be coded in Area A.

CONFIGURATION SECTION EXAMPLE

ENVIRONMENT DIVISION.

CONFIGURATION SECTION.

SOURCE-COMPUTER. IBM iSeries.

OBJECT-COMPUTER. IBM iSeries.

INPUT-OUTPUT SECTION

• The INPUT-OUTPUT SECTION optionally follows the CONFIGURATION SECTION– It supplies information concerning the

input and output devices used in the program by means of a FILE-CONTROL paragraph.

• In the FILE-CONTROL paragraph, a file-name is designated and assigned to a device for each file used in the program.

• The FILE-CONTROL paragraph consists of SELECT statements

– each is coded in Area B followed by a period.

• A SELECT statement

– defines a file-name.

– assigns a device name to that file*.

A file is the major collection of data for a given application.

•Batch processing applications have an input file and an output file.

• Interactive processing allows input using a keyboard;

– therefore, it is not necessary to establish an input file.

• If the output is printed or saved on disk, an output file must exist in the ENVIRONMENT DIVISION.

• If the output is displayed on a screen, then no file declaration is necessary in the ENVIRONMENT DIVISION.

- When this is the case, the ENVIRONMENT DIVISION may be entirely omitted.

ASSIGNING FILES TO DEVICES IN THE ENVIRONMENT DIVISION

OVERALL FORMAT

• The instruction format for the SELECT statement follows:

SELECT file-name-1

ASSIGN TO implementor-name-1

[ORGANIZATION IS LINE SEQUENTIAL]– The implementor-name is a machine-

dependent device specification that is typically provided by the computer center.

OVERALL FORMATREVIEW OF INSTRUCTION FORMAT RULES

1. Uppercase words are reserved words; lowercase words are user-defined.

2. Underlined words are required in the statement.

3. Two lines are used for a SELECT statement– the second line is indented for “

readability”

OVERALL FORMAT

File-Name Rules

1. The file-name assigned to each device must conform to the rules for forming user-defined words.

2. A user-defined word is a word chosen by the programmer to represent some element in a program such as a file-name:

OVERALL FORMAT• Rules for Forming User-Defined

Words (Such as File-Names)

1. 1 to 30 characters.

2. Letters, digits, and hyphens (-) only.

3. No embedded blanks

– It is best to use hyphens to separate words (e.g., EMPLOYEE-NAME)

4. At least one alphabetic character.

OVERALL FORMAT

5. May not begin or end with a hyphen.

6. No COBOL reserved words such as DATA, DIVISION, etc.

• A full list of reserved words appears in Appendix A and in the COBOL Syntax Reference Guide.

THE NET

If you do not have a COBOL Syntax Reference Guide, it can be downloaded from:

http://www.wiley.com/cobol/

OVERALL FORMAT

• A SELECT statement must be specified for each file in the program,.

• If a program requires a disk file as input and produces a printed report as an output file, two SELECT statements will be specified. – one file-name will be assigned to the

disk file

– the other to the print file.

DEBUGGING TIP

• File names assigned by the programmer should be meaningful.

Examples: SALES-IN

SALES-REPORT-OUT

OVERALL FORMAT Implementor-Names or Device Specifications

• Most systems enable the programmer to access frequently used devices by special device names.

OVERALL FORMAT Implementor-Names or Device Specifications

The following are common shorthand device specifications that you will use on our iSeries system:

Printer PRINTER followed by a printer file object name

Disk DISK followed by a file or database object name

SELECT Statements for PCs

1. Device Specification on PCs

(a) The drive on which the disk file appears followed by a colon (e.g., C:, D:, etc.).

• If your file is in a subdirectory, you must specify that as well (e.g., C:\COBOL).

SELECT Statements for PCs(b) The file-name for that disk file, where

the rules for forming file- names are dependent on the operating system.

– The device name for these PC versions of COBOL is usually enclosed in quotes:

SELECT EMPLOYEE-FILE

ASSIGN TO 'C:EMPFILE'.

SELECT INVENTORY-FILE

ASSIGN TO 'C:\INVENTORY\INVFILE.DAT'.

SELECT Statements for iSeries

1. Device Specification on the iSeries

(a) Refer to the file object name. i.e., assume there is physical file named ROSTER that you want the program to access …

You will code

SELECT ROSTER-FILE-INASSIGN TO DISK-ROSTER.

CHAPTER SLIDES END HERE

CHAPTER SUMMARY

COMES NEXT

CHAPTER SUMMARYI. The IDENTIFICATION DIVISION

A. The IDENTIFICATION DIVISION and its paragraphs are used for documentation and do not affect the execution of the program.

B. The first two items to be coded in a program are: IDENTIFICATION DIVISION.

PROGRAM-ID. program-name.

C. A program name that is up to eight characters, letters and digits only, is acceptable on all computers.

CHAPTER SUMMARYE. Comments can be included in the

IDENTIFICATION DIVISION, as well as all other divisions, by coding an * in position 7. – This makes the entire line a comment.

– We encourage you to use comments throughout your programs for documentation.

F. A slash (/) in column 7 will cause the subsequent lines to be printed on the next page of the source listing.

CHAPTER SUMMARY II. The ENVIRONMENT DIVISION

A. The format for the ENVIRONMENT DIVISION is:

ENVIRONMENT DIVISION.

CONFIGURATION SECTION.

SOURCE-COMPUTER. computer-name

OBJECT-COMPUTER. computer-name

INPUT-OUTPUT SECTION.

FILE-CONTROL.

SELECT file-name-1

ASSIGN TO implementor-name-1

CHAPTER SUMMARY II. The ENVIRONMENT DIVISION

• Fully interactive programs that use keyed data as input and screen displays as output are not required to have an ENVIRONMENT DIVISION.

CHAPTER SUMMARYB. The CONFIGURATION SECTION is

usually optional and we recommend you omit it.

It supplies documentary information on the computer(s) being used.

C. The INPUT-OUTPUT SECTION is also

optional but must be included if files are assigned to devices in a program.

We will always include the INPUT-OUTPUT SECTION for batch processing.

CHAPTER SUMMARY

D. The ENVIRONMENT DIVISION is the only division of a COBOL program that may vary depending on the computer used. – Obtain the exact device

specifications or disk file-name rules from your computer center or your instructor.

THE NET

If you do not have a COBOL Syntax Reference Guide, it can be downloaded from:

http://www.wiley.com/cobol/

chapter 2 cobol language fundamentals

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