this can be solved like this

Code:
#include<stdio.h>
#include<conio.h>
int main(){
    int i=0;
printf("enter key a to stop running");
char a='o';
while(a!='a'){
    while(!kbhit()){
        printf("\n%d",++i);
    }
    a=getch();
}

printf("\nyou pressed a and stopped the process!!!");
getchar();
}