Every programming language is designed with some system-defined set of characters, symbols, keywords, and standards. Similarly, COBOL has its own set of characters, symbols, keywords, and standards. Below are the basic and known terms in the COBOL –

• Character set
• Character strings
  • COBOL Words
  • Variables
  • Literals
  • Constants
  • Figurative Constants
  • Comments
• Separators

Character set

The character set refers to the collection of valid characters. They define literals, variables, and other identifiers in a COBOL program.

The COBOL language has its own set of valid characters (78) that contains alphabets (A-Z | a-z), digits (0-9), and special characters. The list of basic COBOL characters is as follows –

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

Character Strings

The character string is a set of characters created for a purpose or to name something. Character strings creates -

• COBOL Words
• Variables
• Literals
• Constants
• Figurative Constants
• Comments

COBOL Words

A COBOL word is a set of characters, and each character is from the following character set -

• Latin uppercase letters A through Z
• Latin lowercase letters a through z
• digits 0 through 9
• - (hyphen)
• _ (underscore)

COBOL word minimum length is one character, and the maximum is 30 characters.

Rules -

• Each lowercase alphabet is equivalent to its uppercase.
• The hyphen(-) or underscore(_) cannot appear as the first or last character.

COBOL Word Types -

COBOL words are two types, and those are -

• User-defined Words - Any word that is defined by the developer is called as a user-defined word and is used to store the data. It can be of maximum length is 30 bytes (except for level-numbers). They can be anything from MTHPROG1, STD-GENDER, reflecting the unique aspects of your COBOL program. For Example - MTHPROG1, STD-GENDER, ....
• Reserved Words - A reserved word is a system-defined word with proper meaning or task assigned in COBOL language. Reserved words can be - keywords, optional words, figurative constants, special character words and special registers. For Example - ACCEPT, SKIP1, ZEROS, ....

Variable

A Variable is used to store and process the value. It holds a pointer to memory location where actually the value stored. Every variable should be declared in the DATA DIVISION of the COBOL program.

A variable declaration should always contain the data type with its length (except the group variable). A Variable is also called a data item. For Example - WS-A, WS-VAR, WS-TOTAL, WS-INPUT, WS_OUTPUT, etc.

Literal

The literal is the value that is assigned to the variable. The value can be a string or number. Literals are two types –

• Non-numeric literals - Non-numeric literals are the strings enclosed by quotation marks(") or apostrophes('). It can contain all valid character that are allowed by COBOL.
  For Example - "HELLO", "THIS ISN'T WRONG", etc.
• Numeric literals - A numeric literal is a number that is a combination of a sign (+ or -), and a decimal point. A numeric literal codes directly without quotation marks(" ") and apostrophes(' ').
  For Example - 1234, -1234, etc.

Constant

A variable is initialized with a literal. If the variable value doesn't change during the program's execution, the variable is considered as a constant variable, and the value is considered as a constant value.

Constant values are three types and those are –

• Numeric constants – Numeric variables having one value throughout the program execution are called numeric constants. 3.14 is numeric constant .
  For Example - 01 WS-PI PIC 9(2)V9(2) VALUE 3.14.
• Alphanumeric | non-numeric constants – Alphanumeric variables with only one value throughout the program execution are called alphanumeric constants. HI is the non-numeric constant.
  For Example - 01 WS-HI PIC X(05) VALUE "HI".
• Figurative Constants - System-defined constants are predefined in the COBOL and used as replacements for standard values like spaces, zeroes, etc. ZEROES is the figurative constant.
  For Example - 01 WS-VAR PIC 9(5) VALUE ZEROES.

Figurative Constant

Figurative constants are system-defined keywords with predefined values. The figurative constants in COBOL are -

Figurative constant	Description
ZERO, ZEROS, ZEROES	Represents one or more occurrences of the numeric value 0. ZERO is a single 0 and ZEROS or ZEROES means two or more occurrences of 0s.
SPACE, SPACES	Represents one or more occurrences of the space. i.e., " " or X'40'. SPACE is single SPACE (" "), and SPACES means two or more occurrences of space.
HIGH-VALUE, HIGH-VALUES	Represents one or more occurrences of the high-value. i.e., X'FF'.
LOW-VALUE, LOW-VALUES	Represents one or more occurrences of the low-value. i.e., X'00').
QUOTE, QUOTES	Represents one or more occurrences of quotation mark (") or apostrophe (').
ALL	Represents one or more occurrences of the character string or figurative constant.

Comments

A comment is a non-executable statement that provides the information about code or business requirements. All computer-supported characters are allowed to write comments, and they do not affect the program's execution.

These are three types based on their usage and where they are used -

• IDENTIFICATION DIVISION Comments - Entries with optional paragraphs in IDENTIFICATION DIVISION are comments and their usage is -
  

         AUTHOR. NameOfProgrammer.
         INSTALLATION. Development-center.
         DATE-WRITTEN. mm/dd/yy.
         DATE-COMPILED. mm/dd/yy. HH:MM:SS.
         SECURITY. Program-type.

• Full line comments (any division)
  
  Any line starting with an asterisk (*) in column 7 (indicator area) is a full-line comment. Comments can be coded in any division.For example -

  ----+----1----+----2----+----3----+----4----+----5
        * FULL LINE COMMENT WITH * IN COLUMN-7.

• Floating comment indicator (*>) -
  
  Comment starts in the middle of any line between 8-72 columns. For Example -

         01 WS-VAR        PIC X(12).    *> INLINE COMMENT   

Separators

A separator is a single or multiple character that separates words or strings. The table below shows the separators list -

Separator	Meaning	Separator	Meaning
	Space	:	Colon
,	Comma	"	Quotation mark
.	Period	'	Apostrophe
;	Semicolon	==	Pseudo-text delimiter

Practical Example -

Scenario - Below screenshot describes the different types of character strings in COBOL programming.

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