A variable provides us with named storage that our programs can manipulate.
Each variable in C++ has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.
The name of a variable can be composed of letters, digits, and the underscore character.
It must begin with either a letter or an underscore.
Upper and lowercase letters are distinct because C++ is case-sensitive:
There are following basic types of variable in C++
|bool||Stores either value true or false.|
|char||Typically a single octet(one byte). This is an integer type.|
|int||The most natural size of integer for the machine.|
|float||A single-precision floating point value.|
|double||A double-precision floating point value.|
|void||Represents the absence of type.|
|wchar_t||A wide character type.|
C++ also allows to define various other types of variables, which we will cover in subsequent chapters like Enumeration, Pointer, Array, Reference, Data structures, and Classes.
A variable definition means to tell the compiler where and how much to create the storage for the variable.
Here, type must be a valid C++ data type including char, w_char, int, float, double, bool or any user-defined object, etc., and variable_list may consist of one or more identifier names separated by commas. Some valid declarations are shown here:
int i, j, k; char c, ch; float f, salary; double d;
The line int i, j, k; both declares and defines the variables i, j and k; which instructs the compiler to create variables named i, j and k of type int.
Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an (=)equal sign followed by a constant expression as follows:
type variable_name = value;
externint d =3, f =5; // declaration of d and f. int d =3, f =5; // definition and initializing d and f. byte z =22; // definition and initializes z. char x ='x'; // the variable x has the value 'x'.