Download - COBOL - Introduction
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COBOL (Common Business Oriented Language)
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Introduction
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History
1959 – Conference on Data System Languages (CODASYL)
created the first standardized business computer programming language
1960 – First proposal for COBOL – named COBOL-60
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History
1961 – First COBOL compilers are getting used
1965 – The usage of COBOL starts to increase a lot (COBOL edition
1965).
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History
1968 – The American National Standards Institute (ANSI) sets the first official COBOL: COBOL-68.
1970 – The International Organization for Standardization (ISO) makes ANSI’s COBOL-68 an
international standard.
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History
1973 – Machine Independent COBOL presented.
1974 – ANSI published a revised version of (ANSI) COBOL, COBOL-74.
1985 – The new COBOL-85 standard is set (ANSI X3.23-1985).
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History
1989 – Intrinsic functions are added to the standard (ANSI
X3.23a- 1989). 1997 – Object-oriented features are
added to Structured COBOL.
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History
2002 – The long awaited object oriented COBOL 2002 standard is set.
– Information on 2008 COBOL standard at http://www.ansi.org
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Features
As a programming language Oriented towards business applications Supports Procedural Programming (from
COBOL-60) Supports Structured Programming (from
COBOL-68)
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Features
As a programming language Supports Machine Independent
Programming (from COBOL-73) Supports Object oriented programming
(from COBOL-2002)
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Features
As a high-level language English like Problem oriented Self-documenting Multi-platform support Easy to learn/read/write and maintain
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Program Structure
PROGRAM
DIVISIONS
SECTIONS
PARAGRAPHS
ENTRY SENTENCES
STATEMENTCLAUSE
PHRASEWORDS CHARACTERS
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Character Set
Digits (10) 0, 1-9 Letters (26) A, B…Z Blank Space (01) b Symbols (12) + - * / , . ( ) = $ ; “ Conditional (02) < >
Total: 51 Characters in COBOL-74
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Character Set
Reference Modifier (01) :Total: 52 Characters in COBOL-85
Apostrophe (01) ‘Total: 53 Characters in Mainframe COBOL
Note: Mainframe COBOL also includes small letters (a to z), for nonnumeric literals.
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Reserved Words
Keywords The spelling of words are American
English and not British COBOL supports abbreviations in many
cases
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User Defined Words
Should not be a Reserved Word 1 - 30 characters Letters, digits, hyphens (-) only At least one Letter or Hyphen
(Recommended to use the first character as an alphabet)
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User Defined Words
Hyphen/s should be embedded. Spaces are not allowed. Must be unique within a set
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Literals
User defined constants Can be Numeric literal, Floating point
literal and Non-numeric literal
Note : A non-numeric literal can hold a character which is not available in COBOL character set.
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Literals
Numeric Literals May consist of numerals decimal point (.)
1 decimal character is allowed Should not be the rightmost character
plus or minus sign 1 sign character (+ or -) is allowed Leftmost character
Not enclosed in quotes
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Literals
Numeric Literals
123 123.45 -256 +2987
Examples
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Literals
Floating Point Literals Support a much wider range of values
than numeric literal
In Mathematics In COBOL12345000 1.2345*107 1.2345E07 or
+12.345E+06
Example
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Literals
Non-Numeric Literals Enclosed in quotes (“) May consists of alphanumeric characters 1 – 160 characters An embedded quotation mark must be
represented by a pair of quotation marks (“ “)
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Literals
Non-Numeric Literals The opening delimiter (“) cannot split
across lines.
Note: COBOL-74 compilers accept only 120 characters.
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Figurative Constants
Predefined constants, but reserved words
Except ZERO/ZEROES, others are treated as Non-Numeric Literals
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Figurative Constants
ZERO, ZEROS, ZEROES (0)QUOTE, QUOTES (“)SPACE, SPACESALL Represents 1 or more occurrences of
the string*Not used in Mainframe
Examples
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Figurative Constants
NULL, NULLS To indicate an invalid address for a POINTER variable;Has the value Zero in Mainframe COBOL
Examples
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Figurative Constants
HIGH-VALUE, HIGH-VALUES Highest value in the collating sequence
Examples
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Figurative Constants
LOW-VALUE, LOW-VALUES Lowest ordinal position in the collating sequence
Examples
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Figurative Constants
NOTES: The singular and plural forms of a figurative
constant can be used interchangeably.Do not use QUOTE/QUOTES to enclose a Non-numeric literal.ZERO, ZEROS, ZEROES are considered as Numeric Literals.
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Special Registers
Reserved words that name storage areas generated by the compiler
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Special Registers
RETURN-CODE Used to pass a return code to the calling
program or to the JCL when the current COBOL program ends
Examples
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Special Registers
WHEN-COMPILED Contains the date at the start of the program compilation
Examples
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Operators
Arithmetic Operators Relational Operators Logical Operators
Note: All COBOL operators must be preceded and followed by a space.
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Operators
Arithmetic Operators Binary Operators
Addition + Subtraction - Multiplication * Division / Exponentiation **
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Operators
Arithmetic Operators Unary Operators
Positive + (Equals to Multiplication by +1) Negative - (Equals to Multiplication by +1)
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Operators
Relational Operators Less Than < Greater Than > Equal To = Less Than or Equal To <= Greater Than or Equal To >=
Note: Each relational operators can be combined with the NOT logical operator
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Operators
Logical Operators Conjunction AND Inclusive OR Negation NOT
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Separator String
A word formed by 2 or more contiguous characters
1st character is a special character and the 2nd character is a space.
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Separator String
Separator comma ,bSeparator period .bSeparator Semicolon ;b
Note: b indicates a blank space.
Examples
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Separator String Rules
A COBOL statement may use Separator Period or
Separator Comma or Separator Semicolon.
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Separator String Rules
The following must end with a separator period: Sentence File (FD), sort/merge file (SD) and data description
entries in the data division Each paragraph in the Identification division
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Separator String Rules
The following must end with a separator period: SOURCE-COMPUTER, OBJECT-COMPUTER,
SPECIAL-NAMES and I-O-CONTROL paragraphs in the Environment division
Each file-control entry in the FILE-CONTROL paragraph
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Separator String Rules
The following must end with a separator period: All the 4 division headers All the section headers
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Phrase & Clause
Phrase – “meaningless” collection of COBOL words Clause – collection of words or phrases that itself has a meaning like
Statements
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Phrase & Clause
Phrase
AT END UNTIL A > B
Clause
OCCURS 5 TIMES LABEL RECORDS ARE STANDARDS
Examples
Examples
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Statement & Clause
Statements – group of words and/or phrases in PROCEDURE DIVISION
Clause – group of words and/or phrases in DATA, ENVIRONMENT &
IDENTIFICATION DIVISION
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Sentence & Entry
Sentence – collection of statements Entry – collection of clauses
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Sentence & Entry
Must be terminated by a Separator Period A COBOL Sentence can have only one
COBOL Statement
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Paragraphs
Subgroup of Sections
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Paragraphs
2 types: Predefined
IDENTIFICATION DIVISION & ENVIRONMENT DIVISION have only predefines paragraphs
User defined PROCEDURE DIVISION allows to define user defined paragraphs
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Paragraphs
Paragraph header has the para-name followed by a separator period.
At least one paragraph should be specified in PROCEDURE DIVISION, if it has any sentences.
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Sections
Subgroup of Divisions
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Sections
2 types: Predefined
ENVIRONMENT DIVISION & DATA DIVISION have only predefines sections User defined
PROCEDURE DIVISION allows to define user defined sections
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Sections
A section header has the: Section-name Followed by a space The word SECTION A separator period
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Sections
Optional, but must be specified in ENVIRONMENT DIVISION and DATA DIVISION, if they have appropriate entries
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COBOL Coding Sheet
Cols 1 – 6 : Sequence Number / Line Number Area, Margin L is Column 1 : Originally designed for entering line numbers on Punch Cards
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 1 – 6 : Used to label a source statement like revision number : Can consist of any characters : Nothing to do inside the program
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Col 7 : Can have the ff: * - designates entire line as comment - - indicates continuation of nonnumeric literal / - forces page break when printing source listing : Also known as Margin C
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Col 7 : A D or d indicates a debugging line : Should be left blank if this line is not a comment/ debugging line/ page break or a continuation.
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 8 – 72 : For COBOL program statements
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 8 – 11 : Area A / Margin A is column 8
: The following items must begin in Area A:- Division headers- Section headers
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 8 – 11 : The following items must begin in Area A:- Paragraph-names- Level indicators FD & SD- Level-numbers 01 and 77
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 8 – 11 : The following items must begin in Area A:
- DECLARATIVES and END DECLARATIVES
- End Program statement
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 12 – 72 : Area B / Margin B is column 12 and Margin R is
column 72
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 12 – 72 : The following items must begin in Area B:
- Entries & Sentences- Statements &
Clauses- Continuation lines
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Note : Anything that begins anywhere in Area A
or B is considered to be in Area A or B respectively.
Level Numbers other than 01 & 77 can begin in Area A or Area B.
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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COBOL Coding Sheet
Cols 73 – 80 : Identification Field (used in punch cards, but no more!)
Note : 80 columns can COBOL accepts and only the first 72 columns are used by the COBOL compiler.
1 – 6 7 8 – 11 12 – 72Sequence No. Indicator No. Area A Area B
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Sample COBOL Program---1----+----2----+----3----+----4----+----5----+----6----+----7----+----8 IDENTIFICATION DIVISION. PROGRAM-ID. SequenceProgram. AUTHOR. Michael Coughlan.*This prgram lets the user to input 2 numbers to be multiplied and display*the product.
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. CalculateResult. ACCEPT Num1. ACCEPT Num2. MULTIPLY Num1 BY Num2 GIVING Result. DISPLAY "Result is = ", Result. STOP RUN.
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Reading the Syntax Diagrams Words in uppercase are reserved words.
When underlined they must be present when the operation of which they are a part is used. When they are not underlined the used for readability only and are optional. If used they must be spelt correctly.
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Reading the Syntax Diagrams Words in lower case represent names which will be devised by the programmer.
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Reading the Syntax Diagrams When enclosed in braces { }
A choice must be made from the options within the braces. When enclosed in square brackets [ ]
Indicates that the material is an option
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Reading the Syntax Diagrams The ellipsis symbol ‘...’ indicates that the preceding syntax element may be repeated at the programmer’s discretion.