Figure 10.9  Recursive Function multiply with Print Statements to Create Trace and Output from multiply(8, 3)
/*
 *  ***  Includes calls to printf to trace execution ***
 *  Performs integer multiplication using + operator.
 *  Pre:   m and n are defined and n > 0
 *  Post:  returns m * n
 */
int
multiply(int m, int n)
{
      int ans;

  printf("Entering multiply with m = %d, n = %d\n", m, n);

      if (n == 1)
            ans = m;     /* simple case */
      else
            ans = m + multiply(m, n - 1); /* recursive step */
 
  printf("multiply(%d, %d) returning %d\n", m, n, ans);

      return (ans);
}

Entering multiply with m = 8, n = 3
Entering multiply with m = 8, n = 2
Entering multiply with m = 8, n = 1
multiply(8, 1) returning 8
multiply(8, 2) returning 16
multiply(8, 3) returning 24