COBOL
COmmon
Business
Oriented
Language

Work began in 1959 and has never
stopped
CODASYL
Conference on Data Systems
Languages
Primarily Business

Wanted a language designed for their
needs.
The resulting language reflected
business needs and the computing
environment.

File Formatting


You can read to or from records
specifying precision by digit.
While it is different than what we are
used to, it is as powerful as newer
languages for records.
Records



COBOL understands the idea of a
record
Has incorporated support for composite
and atomic attributes from the
beginning
This understanding avoids some of the
more tedious aspects of programming
with records by minimizing parsing.
Computing Environment


Words and Bytes: Many assumptions we
make every day the COBOL
programmer could not rely on.
Environment Division: Specifies to the
compiler and programmer the target
environments.

More or less just comments now, useful for
maintenance.
Punch Card
Changes with Time


Certainly the most difficult part of
COBOL is that all new versions must be
backwards compatible.
It is possible to get nearly 817
keywords (ca.1985)
Artifacts



Program line numbers for program
cards
Spacing (Areas A & B)
While not as familiar or as “clean” as {}
block structures, it does add a visual
structure to a program
Divisions and Sections


Sections subdivide four primary
divisions
Provides a top level organization for
programs. More later.
Procedural Paradigm



Supported but not enforced
Centers mostly on GOTO (and in newer
versions, IF/THEN) All procedures
names are labels.
Newer versions support some OO
features.
FOUR PROGRAM DIVISIONS

IDENTIFICATION DIVISION

ENVIRONMENT DIVISION

DATA DIVISION

PROCEDURE DIVISION
IDENTIFICATION DIVISION

Provides the name of the program, who
wrote it, when and where it was
written, when it was compiled, and
what security precautions(if any) should
be taken to restrict access to the
program or to the file it processes.
Division should end with a set of
English sentences giving a brief
overview of what the program does.
ENVIRONMENT DIVISION

Contains information about the computer(s)
on which the COBOL program will be
compiled and on which the resulting machinelanguage program will be run. It also gives a
COBOL name to each file to be processed and
assigns each file to a specified I/O device.
This information defines the hardware
environment in which programs runs.
DATA DIVISION

Gives a brief description of each file to be
processed, and then gives a detailed layout
for the records in the file. Each field in a
record is described in terms of its length and
its type of data. The DATA DIVISION also
describes in a memory area called WORKINGSTORAGE. All data fields(in file records or in
working-storage) must be described in the
DATA DIVISION.
PROCEDURE DIVISION

The computer is actually instructed as
to what processing is to be carried out.
The directions closely resemble English
sentences.
SIMPLE SAMPLE PROGRAM
000100
000200
000300
000400
000500
000600
000700
000800
000900
001000
001100
101200
101300
101400
101500
101600
IDENTIFICATION DIVISION.
PROGRAM-ID. HELLOWORLD.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SOURCE-COMPUTER. RM-COBOL.
OBJECT-COMPUTER. RM-COBOL.
DATA DIVISION.
FILE SECTION.
PROCEDURE DIVISION.
MAIN-LOGIC SECTION.
DISPLAY “HELLO WORLD!”
STOP RUN.
SAMPLE PROGRAM “ACCEPT_NUM”
000100 ID DIVISION.
000200 PROGRAM-ID. ACCEPT1.
000300 DATA DIVISION.
000400 WORKING-STORAGE SECTION.
000500 01 WS-FIRST-NUMBER PIC 9(3).
000600 01 WS-SECOND-NUMBER PIC 9(3).
000700 01 WS-TOTAL PIC ZZZ9.
SAMPLE PROGRAM “ACCEPT_NUM”
000100 ID DIVISION.
000200 PROGRAM-ID. ACCEPT1.
000300 DATA DIVISION.
000400 WORKING-STORAGE SECTION.
000500 01 WS-FIRST-NUMBER PIC 9(3).
000600 01 WS-SECOND-NUMBER PIC 9(3).
000700 01 WS-TOTAL PIC ZZZ9.
SAMPLE PROGRAM “ACCEPT_NUM”
000900 PROCEDURE DIVISION.
001000 0000-MAINLINE.
001100 DISPLAY 'ENTER A NUMBER: '.
001200 ACCEPT WS-FIRST-NUMBER.
001300*
001400 DISPLAY 'ANOTHER NUMBER: '.
001500 ACCEPT WS-SECOND-NUMBER.
001600*
001700 COMPUTE WS-TOTAL = WS-FIRST-NUMBER + WS-SECONDNUMBER.
001800 DISPLAY 'THE TOTAL IS: ', WS-TOTAL.
001900 STOP RUN.
SAMPLE PROGRAM “ACCEPT_NUM
SAMPLE RUN”
ENTER A NUMBER: 7
ANOTHER NUMBER: 7
THE TOTAL IS: 14
COMPARED TO OTHER
LANGUAGES






“ THE GOOD SIDE”
Self-Documenting
Reserved Words Based on English
Readability
Easy to learn
Business Oriented
Non-proprietary(portable)
COMPARED TO OTHER
LANGUAGES







“ THE BAD SIDE"
No encapsulation and little information hiding
No block structure
All variables are global
Numbers closer to human arithmetic
No recursion
Not designed for graphical user environment
Only best for business applications
SOURCES



http://www.engin.umd.umich.edu/CIS/course
.des/cis400/cobol/seccob.html
Newcomer, Lawrence R.. Theory and Problems of
Programming with Structured COBOL.McGraw-Hill,
Inc. 1984.
http://www.fourmilab.ch/documents/univac/cards.html