Variables and Declarations in C++

Variables in C Plus Plus (C++):

A variable can be defined as “a quantity that varies during program execution”.

A variable is a symbol that represents a storage location in the computer’s memory. The information that is stored in that location is called the value of the variable. One common way for a variable to obtain a value is by an assignment. This has the syntax:

variable = expression

First, the expression is evaluated and then the resulting value is assigned to thevariable. The equal sign “=” is the assignment operator in C++.

Declarations in C++:

A declaration associates a group of variables with a specific data-type. All variables must be declared before they can appear in executable statements.

A declaration consists of a data-type, followed by one or more variable names, ending with a semicolon.

Example:

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int a, b, c; float root1, root2; char flag;

Here,a, b and c are declared to be integer variables, root1 and root2 are floating-point variables and flag is a char-type variables.

These declarations could also have been written as follows:

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int a; int b; int c; float rot1; float root2; char flag;

Initial values can be assigned to variables within a type-declaration. To do so, the declaration must consist of a data-type, followed by a variable name, an equal sign (=) and a constant of the appropriate type. A semicolon must appear at the end, as usual.

Example:

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int c = 12; char star = '*'; float sum = 0.; double factor = 0.123458e-6;

Thus, in above example, c is an integer variable whose initial value is 12, star ia a char-type variable initially assigned the character “*”, sum is a floating-point variable whose initial value is 0. and factor is a double-precision variable whose initial value is 0.123458 x 10^-6.