c Storage Classes

A Storage class in C represents the scope of a variable within the program. The storage classes in C are discussed below:

 

Storage ClassesStorage PlaceDefault ValueScopeLife-timeFeatures
autoRAMGarbageLocalWithin functionDefault storage class.
externRAM0GlobalTill the end of main programVisible to all the programs.
staticRAM0LocalTill the end of main programRetains value between multiple functions call.
registerRegisterGarbageLocalWithin functionFaster access than other variables.

 

Example:

#include<stdio.h>  
void demo()
{    
static int i=0;
register int j=0;
auto int k=0;
i++;    
j++;
k++;
 
printf("i = %d\n", i);    
printf("j = %d\n", j);    
printf("k = %d\n", k);    
}  
 
void main()
{    
demo();   
printf ("\n");
demo();   
printf ("\n");
demo();    
}

Output

i = 1
j = 1
k = 1
 
i = 2
j = 1
k = 1
 
i = 3
j = 1
k = 1
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