4.5 Variable Declarations

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Before you can use a variable in C++, it must be defined in a declaration statement . A variable cannot be used unless it is declared.

A variable declaration serves three purposes:

• It defines the name of the variable.

• It defines the type of the variable (integer, real, character, etc.).

• It gives the programmer a description of the variable.

The declaration of a variable answer can be:

 int answer;     // the result of our expression 

The keyword int tells C++ that this variable contains an integer value. (Integers are defined below.) The variable name is answer . The semicolon is used to indicate the statement end, and the comment is used to define this variable for the programmer.

The general form of a variable declaration is:

   type     name   ;   //   comment   

Type is one of the C++ variable types ( int , float , etc.) Name is any valid variable name. The comment explains what the variable is and what it will be used for. Variable declarations come just before the main( ) line at the top of a program. (In Chapter 9 you will see how local variables may be declared elsewhere.)

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