C Foundation

What is C? C Compiler Installation C Extensions C Compiler C Interpreter C Program Structure

C Basics

C Keywords C Data Types C Identifiers C Variables C Constant C Escape Sequences C Constant and Volatile C Typecast


What is Operator C Comma Operator C Arithmetic Operators C Relational Operators C Logical Operators C Bitwise Operators C Conditional Operators C : : Operator C Operator Priority

Basic IO's

Basic IO's C Formatted Functions C Unformatted Functions C Common Functions

Control Statements

What is Control Statement C if Statement C if else Statement C Nested if Statement C Else if Statement C Break Statement C Continue Statement C Switch Statement C Goto Statement


What is Control Loop C for Loop C Nested for Loop C while Loop C Nested while Loop C do while Loop C Nested do while loop


What is Function C User Defined Functions C Recursion C Passing Parameters


Scope C Local Scope C Global Scope

Storage Classes

What is Storage Class C Auto C Extern C Static C Register


What is Array C One Dimensional Array C Two Dimensional Array C Multi Dimensional Array C Arrays Of Strings


What is String C String Functions


What is Pointer C Pointers Arithmetic C Pointer to Pointer C Pointers and Arrays C Pointers and Strings C Pointer to Functions Void Pointers Null Pointers C Null and Void Pointer


What is Structure C Struct within Struct C Array within Structure C Pointer to Structure C Structure and Function C Enum C Bitfield Structure C Type def


What is Union


What is File C read a file C write a file C File Handling C Error Handling C Low Level Disk I/O C Other file functions

Memory Allocation

What is Memory Allocation C Malloc() C Calloc() C Free() C Realloc() C Coreleft()

C Reference

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C Register Storage Class

What Is Register Storage Class

  • Register variables are similar to auto variables. The only difference is register variables are stored in CPU register instead of memory.
  • Register variables are faster than normal variables. Mostly programmers uses register to store frequently used variables.
  • Programmers can store only few variables in the CPU register because size of register is less.
  • The keyword for a variable to declared under register storage class is register.
Register Storage Class

What Compiler do?

On using register keyword we are forcing the compiler not to use memory to store the data instead use CPU register.


Accessing register variable executes faster than auto variable.


One cannot dereference register variable because it has not any memory address.

Now the equation is straight forward, one cannot comes out with pointer concept using register variable.

Syntax - Register Storage Class

register int m;

C program - Register Storage Class

Let's workout a program to demonstrate register storage class in C.

#include <stdio.h>
int main()
int m1 = 5;
register int m2 = 10;
printf("The value of m1 : %d ",m1);
printf("\nThe value of m2 : %d ",m2);
return 0;
  • The value of m1 : 5
  • The value of m2 : 10


The program illustrates that, the register variable is declared and initialized inside the main function.


Keyword register
Storage Type register
Scope Block Scope
Life Time Static lifetime
Visibility Global/Local
Default Value Garbage value
Default Storage Class No

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