C Storage Classes

Why Storage Class

A storage class defines the scope, visibility and life-time of variables.

Types of storge classes

There are four types of storage classes in c programming. They are

Storage class Defines Scope

We already defined that a scope of a variable is defined by its storage classes.

What is meant by scope?

A scope is defined as the area in which the declared variable is available.In c programing we can encounter five different types of scopes. They are

• program scope
• file scope
• function scope
• block scope
• prototype scope

Program To Define Scope In Storage Classes

Let's workout a program to explain all 5 different scope in storage class.

C program - Storage Class

#include <stdio.h>
void display(int num);
// here 'num' has prototype scope
static void fun();
int main()
{
int num=2;
void display(int d){
// here 'display' has program scope
printf("\n%d", d);
}
display(1);
fun();
bark:{
//here 'bark' has function scope
int i = 0;
printf("\nBow Bow");
if(i = 1){
return 0;
}
i++;
}
goto bark;
return 0;
}
static void fun(){
//here 'fun' has file scope
int i = 0;
//here 'i' has block scope
printf("\n%d", i);
i++;
}

Storage class Defines Visibility

We already defined that visibility of a variable is defined by its storage class.

What is meant by Visibility?

Visibility is the way of hidding or showing a variable inside or outside a scope. Visibility is otherwise said to be accessibility.

Program To Define Visibility In Storage Classes

Let's workout a simple program to explain visibility of a variable.

#include <stdio.h>
int main()
{
int i = 9;
//visible inside all function.
void display(){
//visible inside this function only.
int j = 10;
printf("%d",i);
}
display();
printf("%d",j);
return 0;
}

Storage class Defines Life-time

We already defined that life-time of a variable is defined by its storage class.

What is meant by life-time?

Life-time is defined as a period of time in which the variable lives. There are three types of life-times in storage classes. They are

• static life-time
• automatic life-time
• dynamic life-time

Program To Define Life-time In Storage Classes

Let's workout a simple program to explain all 3 life-time in storage class.

#include <stdio.h>
int main()
{
int *numbers = (int*)malloc(4* sizeof(int));
// *number act as a automatic and dynamic as well
static int i;
// i act as a static variable
numbers[0] = 0;
numbers[1] = 1;
numbers[2] = 2;
numbers[3] = 3;
free(numbers);
printf("\nStored integers are ");
for(i = 0; i < 4; i++)
printf("\numbers[%d] = %d ", i, numbers[i]);
return 0;
}

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