Register storage class
To increase your program efficiency or making a fast program we used register variable. Register contain by default garbage and it scope within a bracket.
EX:WAP to use of register
#include<stdio.h>
#include<conio.h>
main(){
register int i;
clrscr();
for(i=0;i<20000;i++)
printf("%d",i);
getch();
}