
102 C++ Declarations
Identifiers are user-defined names and are generally defined in lower case letters. However, the
upper case letters are also permitted. The underscore (_) symbol can be used as an identifier. In gen-
eral, underscore is used to link two words for the long identifiers. Valid identifiers are as follows:
length, area, volume, sUM, Average, etc.
Invalid identifiers are as follows:
Length of line, S+um, year’s, etc.
Rules for defining identifiers are as follows:
(1) The identifier name must begin with a character or underscore and should not start with
digit. No spaces are allowed between the characters in the variable but underscore is