#include <stdio.h>
#include <stdlib.h>

void f(unsigned char a, unsigned int b) { 
   unsigned char *cp, *dp;
   cp = (unsigned char *) calloc(b, 1); 
   for (dp = cp; dp < (cp + b); dp++) 
      *dp = a + dp - cp;
   *dp = '\0';
   printf("String = %s\n", cp);
}

int main()
{
   f('a', 3);

   return 0;
}