Introduction to COBOL
COBOL provides very powerful file handling features. COBOL
features like variable length records, Indexed and sequential files with
unlimited number of records. This makes COBOL very efficient in commercial data
processing. COBOL programs are so much like plain English that even a person
with no programming knowledge would be able to understand a COBOL program. The
same reason also makes COBOL very easy to learn and programs easy to maintain.
COBOL is self-documenting. Which means that very little additional documentation
is required with a COBOL program. COBOL is used on almost all platforms. PC’s,
Minis, Mainframes, all support COBOL. A programmer would have to only look at
some minor differences to shift from one machine to another.
1.1 COBOL Program Layout
1.1.1 Columns 1 to
6 - Line Number
1.1.2 Columns 7th
- Indicator Columns. A ‘*’ is use to comment the line.
1.1.3 Columns 8
to 11 - Area A
1.1.4 Columns 12
to 72- Area B
1.1.5 Column 73
onwards - The compiler ignores whatever is written in these columns
1.2. COBOL program Structure
- COBOL
programs are divided in four divisions.
IDENTIFICATION DIVISION.
ENVIRONMENT DIVISION.
DATA DIVISION.
PROCEDURE DIVISION.
- The
divisions are divided in sections, sections in paragraphs, paragraphs in
sentences and sentences in words. Words are made up of the COBOL character set.
- All
division, section and paragraph names are written in Area A. All sentences are
written in area B.
1.2.1 IDENTIFICATION DIVISION
i.e.
IDENTIFICATION DIVISION.
PROGRAM-ID.
Program-name.
AUTHOR.
ABC.
INSTALLATION. Comment-entry
DATE-WRITTEN. Comment-entry
DATE-COMPILED. Comment-entry
SECURITY.
Comment-entry
The first paragraph of the identification division must be the PROGRAM-ID paragraph. The other paragraphs are optional, but, when written, must appear in the order shown as above.
1.2.2 ENVIRONMENT DIVISION
There is no mandatory entry in this division. There are some entries can be written under this division.
Example:
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SOURCE-COMPUTER. IBM-AS400.
OBJECT-COMPUTER. IBM-AS400.
INPUT-OUTPUT SECTION.