Language basics : identifiers
Identifiers are names of various entities use in a C++ program. Identifiers are used to refer to the data items, functions, classes, objects etc.
C++ identifier is a sequence of letters, digits, and underscore that must begin either with a letter or an underscore.
Certain identifiers are reserved for constructing C++ data and control structures. These are called keywords and cannot used as user identifiers. See inside of front cover for a list of keywords.