// PascalsTriangle.c
// Calculate and display rows of Pascal's Triangle.

#include <stdio.h>

typedef unsigned int WORD;

/* Maximum number of rows in triangle. */
#define MAX 50

/* Number of rows to display. */
#define NROW 20

/* Field width for display of each number. */
#define WIDTH 6

/* Total number of columns to display in. */
#define COL 135

/* Array to hold rows of triangle - seed with first row. */
WORD t[MAX] = {1};

void NextRow(WORD a[]);

void main(void)
{
  int i, j;         /* to index for loops */
  WORD n = 0;

  for (i = 1; i < NROW; i++)
  {
    printf("%*c", (COL-WIDTH*(i+1))/2, ' ');
    for (j = 0; j < NROW; j++)
    {
      if (t[j])
        printf("%*u", WIDTH, t[j]);
      else
        break;
    }
    printf("\n\n");
    NextRow(t);
  } // for i
} // main()


void NextRow(WORD a[])
/*
   USE:  Calculate next row of Pascal's triangle.
   IN:   a[] = last row, padded right with 0's
   OUT:  a[] = next row, padded right with 0's
*/
{
  int i;          /* to index for loop */
  WORD b[MAX];    /* store old row before calc next one */

  /* Copy incoming row into b[]. */
  for (i = 0; i < MAX; i++)
    b[i] = a[i];

  /* Apply addition formula, including 0 on right.*/
  for (a[1] = 1, i = 1; i < MAX; i++)
    a[i] = b[i] + b[i-1];
}