C Variables

A variable in C programming language is a named location in memory that can be used to store data. Variables are declared with a data type and a name. The data type specifies the type of data that the variable can store. The name is used to refer to the variable in the program.

Variable Declaration

Variables must be declared before they are used. The declaration specifies the variable's data type and name. Variable names must start with a letter (a-z, A-Z) or underscore (_) and can be followed by letters, digits (0-9), or underscores.

int age; // Declaration of an integer variable named 'age' double salary; // Declaration of a double variable named 'salary' char grade; // Declaration of a character variable named 'grade'

Variable Initialization

Variables can be initialized (given an initial value) when declared or at a later point in the program. Uninitialized variables contain garbage values, so it's good practice to initialize them before use.

int count = 0; // Declaration and initialization of an integer variable double price = 99.99; // Declaration and initialization of a double variable char initial = 'A'; // Declaration and initialization of a character variable

Variable Assignment

You can change the value of a variable using the assignment operator =.

age = 25; // Assigning a new value to 'age' salary = 55000.50; // Assigning a new value to 'salary' grade = 'B'; // Assigning a new value to 'grade'

Variable Scope

  1. Variables have scope, which defines where they can be accessed within the code.
  2. Local variables are declared inside functions and have function-level scope.
  3. Global variables are declared outside functions and have file-level scope, accessible throughout the entire program.
int globalVar = 10; // Global variable void myFunction() { int localVar = 5; // Local variable // 'localVar' is accessible within this function } // 'globalVar' is accessible from any part of the program

Dynamic Variables (Pointers)

C programming language allows you to work with dynamic memory allocation using pointers, where you can allocate memory for variables at runtime.

int *dynamicVar; // Declaration of a pointer to an integer dynamicVar = (int *)malloc(sizeof(int)); // Allocating memory for an integer *dynamicVar = 42; // Assigning a value to the dynamically allocated integer

Points to remember:

  1. Variables must be declared before they can be used.
  2. Variables can be declared anywhere in the program, but they are typically declared at the beginning of the program.
  3. The scope of a variable is the part of the program where the variable can be used. The scope of a variable is determined by where it is declared.
  4. Variables can be initialized when they are declared. Initialization means assigning a value to the variable when it is declared.
  5. Variables can be changed throughout the program. However, it is important to make sure that the variable is not changed in a way that would cause an error.


In C programming, variables are containers used to store and manipulate data. They are declared with a specific data type, can be initialized with values, and have scope that defines where they can be accessed within the code. Proper use of variables is fundamental for managing data in C programs efficiently and effectively.