Answer L16

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

/* Puzzle L16 -- print a n by m block of stars */
int main()
{
  int row, col;
  int n=7, m=21;
  
  for ( row=0; row < n; row++ )
  {
    for ( col=0; col < m; col++ )
      printf("*");
    printf("\n");
  }
  
  	
  return 0;
}

Comment: This is your basic loop within a loop. The outer loop (the counter is row) counts the rows. The inner loop (the counter is col) counts the characters in the current row.