Introduction to basic concepts of COBOL

1. COBOL
(COMMON BUSINESS ORIENTED
LANGUAGE)
By: Manjula Sanjay
Asst. prof, Dept. of MCA

2. Objective
 COBOL is one of the most widespread commercial applications languages in use
today. The course is aimed at developers to get the basic knowledge of COBOL
program development. This course covers all aspects of Programming with
COBOL.
 The course teaches the design, writing and testing of COBOL programs.
Having studied this subject, the students should be able:
 Develop Structured COBOL Programs
 Understand and Use COBOL Verbs
 Develop COBOL programs using the available verbs
 Develop and Test COBOL print programs
 Develop and Test COBOL programs accessing different types of files

3. Text Books
 Text Book
 Nancy Stern and Robert A Stern, 11th
edition, Structured
COBOL Programming, John Wiley & Sons, 1998.
 Reference Book
 M.K.Roy and D. Ghosh Dastidar, COBOL Programming,
Tata McGraw Hill, 2001, COBOL—85,2nd
Edition.

4. Introduction
 Types of computer programs
 Operating system programs
 Application programs / Software
 Types of Processing
 Interactive – A point-of-Sale system
 Batch processing – Payroll System (Large volume of
input at periodic intervals)
 COBOL support both type of processing
 Customized Application Package: Budget, Scheduling etc.
 Machine language programs
 Symbolic programs : translates to machine language by

5. Program Development Process
 Determine the program specification
 Design the program using program planning tools
 Code the program
 Compile the program
 Test the program
 Document the program
Compile the program
Source program
in symbolic
language
Object program
in machine
language
Translated by
compiler

6. Test the program
 Debug during compile & test phase
 Compile time errors: Syntax error e.g. ADD | AD
 Misspelled reserved words
 Missing punctuation
 Execution errors: Logic error e.g. ADD instead of
Multiply
 Run-Time error: Occurs if computer cannot execute
the instruction.
E.g.-
 Attempt to divide by zero
 Reading from a file that cannot be found.

7. Contents
 History of COBOL
 Features & Language Fundamentals
 Program Structure
 Coding Format for COBOL Programs
 Character Set, Words, Data Names, Literals.

8. Nature of COBOL
 popular Business-oriented language
 Standard language
 English-like language: Standard & business oriented
 Relatively easy to understand- User friendly
 Reference: http://www.ansi.org

9. History of COBOL
 1959 – United States Department of Defense
 1960 - COBOL initial specifications presented by CODASYL
(COnference on Data SYstems Languages)
 1961 – COBOL 61
 1964 – BASIC COBOL extended to Visual COBOL
 1968 – ANSI (American National Standards Institute) developed
American National Standard (ANS) COBOL
 1974 – ANSI published revised version of (ANS) COBOL
– Business applications needed to manipulate character as
well as numeric data
– String operations added
 1985 – COBOL 85 Standards was introduced with revised
version of COBOL-74.

10. COBOL
 What does COBOL stand for?
COmmon Business Oriented Language.
 Which are target area of COBOL applications?
Defense, Aircraft, Insurance, Finance, Retail
etc.
(file & data oriented applications involved)
 So we can say that COBOL is basically used for writing
business applications and not for developing system
software

11. Future of COBOL
 COBOL is likely to remain an important language in the years
ahead
 According to Datapro Information Services Group
about 150 billion lines of COBOL source code in
use
 5 billion new lines added each year
 Cobol is used by 42.7% of application
programmers in medium to large U.S. companies
 $200 million revenues for 2001

12. Year 2000 Problem (Y2K)
 Year stored as two digits in older programs to save
space
 19 assumed as valid prefix for all years
 95 represented year 1995
 Invalid as prefix for years 2000 and beyond
 00 could mean 1900 or 2000

13. Year 2000 Problem (Y2K)
Many calculations with dates incorrect starting in 2000
 To find your age if you were born in 1970
Subtract 70 from 95 (95 - 70 = 25)
 Calculation incorrect for year 2000 and beyond
00 - 70 = -70 when age should be 30

14. Year 2000 Problem (Y2K)
To correct problem
 Billions of lines of code, many written in COBOL
needed to be examined
 Code changed to use four digits for year
 Age, other calculations now correct
1995 - 1970 = 25
2000 - 1970 = 30
2012 – 1988 = 24

15. Improving Program Design
Two techniques used to develop programs that are easier to
understand, test, debug and modify
 Structured Programming
 Top-Down Programming

16. Structured Programming
 Eliminates use of GO TO statements
 Allowed skipping to different sections of program without
returning to starting point
 Program logic easier to follow with "GO-TO-less"
programming

17. Structured Programming
Program divided into paragraphs
 Structured programming follows logical control constructs
that make program easier to read, modify, and debug.
 Main paragraph or module controls logic flow using
PERFORM statements
 Main module "performs" other modules when instructions in
that module required
 Each module can be written and tested independently of
others

18. Top-Down Programming
 Another technique to make programs easier to understand,
test, debug and modify
 Develop program like term paper
 Develop outline first
 Add details for each of main steps
 Add further refinement for more complex steps

19. Top-Down Programming
For COBOL program
 Code main modules or routines first
 Code intermediate modules next
 Details deferred to minor modules and coded last

20. COBOL – Program Structure
Principal portions of a program.
There are 4 divisions –
a) Identification (Required)
b) Environment (Optional)
c) Data (Optional)
d) Procedure (Required)
User defined chunk of code
which consists of one/more
paragraphs.
e.g.
a) U000-CHECK-LOG SECTION.
b) FILE SECTION.
User defined chunk of code
which consists of one/more
sentences.
e.g.
a) P000-PRINT-FINAL-TOTALS.
b) PROGRAM-ID.
A SENTENCE consists of one or
more statements and is
terminated by a full stop.
e.g. a) MOVE .21 TO VAT-RATE
b) COMPUTE VAT-AMOUNT =
PRODUCT-COST * VAT-RATE.
PROGRAM
DIVISIONS
SECTIONS
PARAGRAPHS
SENTENCES
STATEMENTS
A STATEMENT consists of a
COBOL verb and an
operand or operands.
e.g.
SUBTRACT T-TAX FROM GROSS-
PAY GIVING NET-PAY
CHARACTERS
RESERVED WORDS
USER DEFINED WORDS

21. Example
IDENTIFICATION DIVISION.
PROGRAM-ID. Multiplier.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 Num1 PIC 9 VALUE ZEROS.
01 Num2 PIC 9 VALUE ZEROS.
01 Result PIC 99 VALUE ZEROS.
PROCEDURE DIVISION.
DISPLAY "Enter first number (1 digit) : " .
ACCEPT Num1.
DISPLAY "Enter second number (1 digit) : “.
ACCEPT Num2.
MULTIPLY Num1 BY Num2 GIVING Result.
DISPLAY "Result is = ", Result.
STOP RUN.

22. 1. DIVISIONS
 A DIVISION is the largest unit in the COBOL program and is a
collection of SECTIONs and/or paragraphs. Every COBOL
program is divided into four DIVISIONS.
 IDENTIFICATION DIVISION
 Identifies the program to the computer. It also provide
documentation about the program
 ENVIRONMENT DIVISION
 Define file-names and describe computer equipment used by the
program
 DATA DIVISION
 Describe input and output format used by the program. Also define
constants and work areas necessary for processing the data
 PROCEDURE DIVISION
 Instructions for reading input, processing and creating output

23. 2. SECTIONS
 A SECTION is a collection of related paragraphs.
 The IDENTIFICATION DIVISION doesn’t contain any
SECTIONs, the ENVIRONMENT AND DATA DIVISIONs
have pre-defined SECTIONs that you may or may not
include, depending on the requirement and the
PROCEDURE DIVISION may contain only user defined
SECTIONs.
 A user defined SECTION is indicated by a user-defined word
followed by the reserved word SECTION.
 It is used mainly to divide the executable program into units
that can be loaded and executed independently.
 Thus, a program larger than the memory size can be
accommodated in memory.

24. 3. PARAGRAPHS & 4. SENTENCES
3)
 A paragraph is a collection of sentences that form a
logical unit in a COBOL program.
 It is the basic unit of organisation of a COBOL
program and is referred by a user-defined name in
the program.
4)
 A sentence is a sequence of one or more statements,
ending with a period.

25. 5. STATEMENTS
 A statement is a valid combination of a COBOL verb and its
operands.
 It specifies an action to be taken by the object program.
 The COBOL statements can be broadly classified into two
types -
 Imperative statements
 An imperative statement begins with a verb and
specifies an unconditional action to be taken.
 Conditional statements.
 A conditional statement is one in which the action to be
taken is determined by some condition that is evaluated
when the program is executed.

26. 6. RESERVED WORDS
 A reserved word is a character-string with a predefined
meaning in a COBOL source program.
 There are several types of reserved words in COBOL.
 Keywords:- appear in uppercase.
 Eg ADD, READ etc
 Optional Words:- They improve readability.
 Eg GIVING, AFTER etc
 Figurative constants:- Refer to constant values.
 Eg ZEROES, SPACES etc

27. 7. USER DEFINED WORDS
 They are constructed and used by the application
programmer.
 They are normally used to define paragraph names,
SECTION names, file names, temporary variables,
etc.,
 The following are the rules for forming user-defined
words.
 Length may be up to 30 characters.
 Only letters, digits and hyphen (-) are allowed.
 Embedded blanks are not allowed.
 At least one character must be alphabetic.
 Cannot be COBOL reserved words.
 May not begin or end with hyphen.

28. 8. CHARACTERS
 The most basic and indivisible unit of the COBOL
language is the character.
 The COBOL character set includes 78 characters that can
be classified as letters of the alphabet, digits and special
Characters.

29. COBOL coding sheet
Column numbers
1 2 3 4 5 6 7 8 9 10 11 12 13 14 . . . . . . . 72 80
Column
numbers
* Area A Area B
I
D
E
N
T
I
F
I
C
A
T
I
O
N
A
R
E
A
-
/

30. COBOL coding rules
 Each line is considered to be made up of 80 columns.
 Columns 1 to 6 are reserved for sequence numbers.
1 to 3 ---Page Number. 4 to 6 ---Line Number
 Column 7 is an indicator column and has special
meaning to the compiler.
Hyphen ( - ) indicates continuation.
Slash ( / ) indicates comment line , forces page break when
printing source listing.
Asterisk ( * ) indicates comment line, no such page ejection.
 Columns 8 to 11 are called Area A. All COBOL DIVISIONs,
SECTIONs, paragraphs and some special entries must begin in
Area A.
 Columns 12 to 72 are called Area B. All COBOL statements must
begin in Area B.

31. COBOL coding sheet
Almost all COBOL compilers treat a line of COBOL
code as if it contained two distinct areas. These are -
AREA A
*) Between Column 8 to 11
*) Division, Section, Paragraph
names, FD entries & 01
level entries must start in
Area A
AREA B
*) Between Column 12 to 72
*) All Sentences & Statements
start in Area B

32. coding rules
 Columns 73 to 80 are identification area. Anything written in
this area , will be ignored by the compiler but will appear in the
source listing.
 Columns 1-6 and 73-80 optional and rarely used today
 Column 7 for continuation, comment, starting new page
 Columns 8-72 for COBOL program statements
Column 7
/ (slash) forces page break when printing source listing
* (asterisk) designates entire line as comment
- (dash) to indicate continuation of nonnumeric literal

33. Margin Rules
 Columns 8-72 divided into two areas
 Area A - columns 8, 9, 10, 11
 Area B - columns 12-72
 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
 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

36. COBOL CHARACTER
SET
Overview

37. Character Meaning
Space
+ Plus sign
- Minus sign or hyphen
* Asterisk
/ Forward slash or solidus
= Equal sign
$ or £ Currency sign
, Comma
; Semicolon
. Decimal point or period
" Quotation mark
( Left parenthesis
) Right parenthesis
> Greater than
< Less than
A-Z (26) Alphabet (uppercase)
a-z Alphabet (lowercase)
0-9 (10) Numeric characters

38. COBOL Words
 0-9 , A-Z and - Hyphen
 The total no of character must not be greater than 30.
 One of the character must be a letter.
 A word cannot begin with Hyphen.
 A word must not contain a blank or special character except
Hyfen (-)
 A Cobol word can be User defined or reserve word
Valid words Invalid Words
GROSS-PAY -Gross-
OVERTIME-HOURS OVERTIME HOUR
A 1-2-3
B12-4 More than 30 characters

39. Data names and Identifiers
 Data names are named memory locations.
 Data Names must be described in the DATA DIVISION before
they can be used in the PROCEDURE DIVISION.
 Can be of elementary or group type.
 Can be subscripted for Arrays.
 Are user defined words.
 Ingle data name or a data name qualified, indexed or
subscripted is normally referred to by the general term
identifier.
 Valid data names: A12 sum-natural net-pay
 Invalid: DATA ADD 45 46+2A

40. Rules for forming User-defined words/Data
names
 Can be at most 30 characters in length.
 At least one alphabetic character.
 Only alphabets, digits and hyphen are allowed.
 Blanks are not allowed.
 May not begin or end with a hyphen.
 Should not be a COBOL reserved word like
ADD,SUBTRACT,MOVE,DISPLAY etc….

41. Data-Name Guidelines
1. Use meaningful data-names that describe contents of field
2. Use prefixes or suffixes in data-names when appropriate
• -IN and -OUT for fields (Emp-Salary-IN and Emp-Salary-
OUT)
• -FILE and -RECORD for file and record names
• Emp-File or Emp-Record
• Amount-Due-In instead of A1

42. Identify the valid data-names
• Identify the valid data-names
1. Date-Of-Birth
2. Amount$Out
3. -First-Name
4. 98-6
5. Time out
6. ADD

43. Literals
 Literals are symbols whose value does not change in a program.
 A data name may have different values at different points of time
whereas a literal means the specific value which remains
unchanged throughout the execution of the program. For this
reason a literal is often called a constant.
Example--- MOVE 0 to sum. (Here 0 is literal)
 There are 3 types of literals namely
(1) Numeric literals.
(2) Non-numeric literals.
(3) Figurative constants.

44. Rules for Numeric Literals
1. A numeric literal can be formed with the help of digits only.
2. The maximum number of digits allowed in a numeric literal
varies from compiler to compiler. can have a maximum of
18 digits.
3. + or - sign may be included to left of first digit.
4. Decimal point permitted within literal. May not follow last
digit.
Valid numeric literals
23 , +2359.4 , .125 , -68734

45. Rules for Nonnumeric Literals
• Composed of characters which are enclosed within quotation
marks.
• Generally used for output messages or headings.
• Any character in COBOL character set except quotation mark.
• The maximum number of characters that are allowed is compiler
dependent. ANSI 74: 120 characters.
Valid Nonnumeric Literals
“123 Main St.” “$14.99”
“12,342” “Enter a value from 1 to 10”

46. Figurative Constants
 These are literals representing values that may be frequently
used by most programs.
 These are given some fixed names and when the compiler
recognizes these names it sets up the corresponding values
in the object program.
 Example--- MOVE ZERO TO sum.
 MOVE SPACES TO REPORT-REC.
 The following is the list of figurative constants and their
meanings.

47. Figurative constants Meaning
ZERO(S) or ZEROES Represents the value 0, one or
more depending on the context
SPACE(S) Represents one or more spaces
HIGH-VALUE(S) Represents the highest value
LOW-VALUE(S) Represents the lowest value
QUOTE(S) Represents single or double
quotes
ALLALL literalliteral Fill With Literal
Literals – Figurative Constants

48. Figurative Constants - Examples
01 GrossPay PIC 9(5)V99 VALUE 13.5.
MOVE TO GrossPay.
01 GrossPay PIC 9(5)V99 VALUE 13.5.
MOVE TO GrossPay.
ZERO
ZEROS
ZEROES
01 StudentName PIC X(10) VALUE "MIKE".
MOVE ALL "-" TO StudentName.
01 StudentName PIC X(10) VALUE "MIKE".
MOVE ALL "-" TO StudentName.
StudentName
M I K EM I K E 
GrossPay
0 0 0 1 3 5 0


49. Figurative Constants - Examples
01 GrossPay PIC 9(5)V99 VALUE 13.5.
MOVE TO GrossPay.
01 GrossPay PIC 9(5)V99 VALUE 13.5.
MOVE TO GrossPay.
ZERO
ZEROS
ZEROES
01 StudentName PIC X(10) VALUE "MIKE".
MOVE ALL "-" TO StudentName.
01 StudentName PIC X(10) VALUE "MIKE".
MOVE ALL "-" TO StudentName.
StudentName
- - - - - - - - - -- - - - - - - - - -
GrossPay
0 0 0 0 0 0 0


50. Continuation of Lines
 A statement or an entry may be continued to the area B of the
next line as and when necessary.
 A hyphen(-) is used in the indicator field for continuation of
lines.
 Actually, a hyphen in the indicator field means that the first non-
blank character in the area B of the current line is the character
immediately following the last non-blank character of the
previous line.
 Example—In case of non numeric literal
Indicator line Area A Area B
Continued line “Enter the
Continuation Line - “Number”.

51.  Is Cobol still used ?
 75% of all business data is processed in COBOL.
 There are between 180 billion and 200 billion lines of
COBOL code in use worldwide.
 15% of all new applications (5 billion lines) through 2009 will
be in COBOL.

52. Thank You