A COBOL word can be formed using the following characters:

0-9
A-Z (a-z)
- (hyphen)

The following rules must be adhered in forming COBOL words:

A word cannot begin or end with a hyphen. A word can have at the maximum 30 characters. One of the characters must be a letter. Some compilers put the additional restrictions that the first character must be a letter. Except hyphen (-) no special character allowed.

Examples
Valid Cobol Word :
EMP-SAL
NET-SALARY
TOT-MARK
N100

Invalid Cobol Word :
-PAY (it starts with a hyphen)
TOTAL MARK (blank space embedded)
COMPUTE (Reserved word)
MULTIPLY (Reserved word)
23 (No letter)

There are 2 types of words in COBOL. A COBOL word can be either a USER-DEFIND WORD or RESERVED WORD. The reserved words are used in COBOL statements and entries for specific purposes by the COBOL compiler.

Some reserved words are given below:
ADD, SUBTRACT, DIVIDE, MULTIPLY, IF, PERFORM etc.

Any attempt by the programmer to declare the reserved word will be indicated as an error during the compilation stage of the program.

A DATA NAME gives reference to the storage space in the memory where the actual value is stored. This value takes part in the operation when that particular data name is used in the PROCEDURE DIVISION.

The actual values can also appear in a program. Such values are known as literals. For Example, the statement MOVE 0 TO TOTAL indicates that the value zero will be moved to the variable TOTAL. This constant 0 which used in the body of the statement is a literal.

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. Moreover the literal is not given a name; it represents itself and does not require to be defined in the DATA DIVISION.

There are 3 types of literals:

a) Numeric Literals
b) Nonnumeric Literals
c) Figurative constants

NUMERIC LITERALS

Example: .125, 12.5

A nonnumeric literal is used in general to output messages or headings. Characters that are enclosed between “ “ constitute nonnumeric literal. The maximum number of characters that are allowed within two quotation marks is compiler dependent.