What is a variable in C Language

A variable may be defined as a named memory location i.e. a variable is the name given to a data item to refer to a memory location. The value of a variable can vary during the execution of a program.

Rules to name a variable in C Language

There are few basics rules which must be kept in mind while defining a variable. They are as follows:-

1. Both digits and alphabets are allowed while naming a variable.
2. First character must be an alphabet or underscore.
3. Variable name can contain digits only after first character.
4. Keyword can’t be used to name a variable.
5. No special character other than underscore can be used.
6. It can’t contain spaces.
7. Capital letters and small letters are treated differently.

Examples of valid variable names

Examples of invalid variable names

 Declaration of Variables

In a C program, the variables must be declared before they can be used The syntax for declaring a variable is :-

<data-type> variable-1,variable-2,variable3;

Here data-type refers to any valid data type of C which may be int, float, char or any user defined data type of C.

variable-1, variable-2, vaiable-3 are name of various variables defined by the programmer.

Example:

 int number;            

Above statement declares a variable named number of int type.

Initialization of Variables  

Initialization refers to assigning some value to a variable during declaration of variable.

Example

 int a=5;

Above statement initializes the variable named a with value 5.

Test Your Knowledge

Q1. Define a variable.
Q2. How can we declare and initialize a variable?
Q3. Which of the following are invalid variable names and why?
(i) Rs1000
(ii) $250          
(iii) Father’s name       
(iv) student-name
(v) Raghav parsad      
(vi)newvalue1  
(vii) India@india.com  
(viii) Factorial

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