Different type of variable in C

 

1. Variable is known as memory location.
2. It is used to store data.
3. Its value can be changed and can reused many times.

Syntax

1. type variable_list;  

Example

1. int a;
2. char b;
3. float c;

Rules for defining variables

1. A variable can have alphabets, digits, and underscore.
2. A variable name can start with the alphabet, and underscore only. 
3. It can't start with a digit.
4. No whitespace is allowed within the variable name.
5. A variable name must not be any reserved word or keyword, e.g. int, float, etc.

Types of Variables in C

1. local variable
2. global variable
3. static variable
4. automatic variable
5. external variable

1. Local variable

• Variable that is declare inside the function or block is known as local variable.
• It is also known internal variable.
• You must have to initialize the local variable before it is used.

Syntax

1. void function()
2. {
3. int a;
4. }

2. Global variable

• Variable that is declare outside the function or block is known as global variable.
• It is also known as external variable.
• Syntax

1. int a;
2. void function()
3. {
4. a=10;
5. }

3. Static variable

• Variable that is declare using static keyword is known as static variable.
• Static variables can be defined inside or outside the function.
• Static variable value can not be changed during the execution of the program.
• Syntax

1. void function()
2. {
3. static int a=10;
4. }

4. Automatic variable

• Variables that can be defined using keyword auto.
• Variables allocate memory automatically.
• Syntax

1. void function()
2. {
3. auto int a=10;
4. }

5. External variable

• Variable that is accessible in multiple c source file .
• We can declare external variable using external keyword.
• Syntax

1. external_var.h
2. external int a=20;

• Example

#include <external_var.h>
#include <stdio.h>

1. void function()
2. {
3. printf("External variable %d",a);
4. }

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