🔺 A Pascal's Triangle Program in C11

pascals-triangle.c

/* 
 * Calculate the binomial coefficients required to represent Pascal's Triangle
 *  after prompting the user for a tree depth value..
 *
 * Derek Callaway [decal (AT) sdf {D0T} org] Tue Jul  4 11:37:30 PDT 2017
 *
 * Compile with: gcc -std=c11 -pedantic -ansi -o pascals-triangle pascals-triangle.c 
 */

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

static unsigned long fact(const unsigned long) __attribute__ ((fastcall, visibility("internal")));

signed int main(void) {
    register unsigned long i = 0;
    auto unsigned long line = 0;

    fputs("*** Enter tree depth as a whole number (i.e. no of lines in triangle): ", stdout);

    scanf("%lu", &line);

    for(;i < line;++i) {
         const unsigned long b = line - i - 1;
         register unsigned long j = 0;

         for(;j < b;++j)
             putchar(' ');

         for(j = 0;j <= i;++j) {
           const unsigned long n = fact(i) / (fact(j) * fact(i - j));

           printf("%lu ", n);
         }

         putchar('\n');
    }

    _Exit(EXIT_SUCCESS);
}

static unsigned long fact(const unsigned long num){
  register unsigned long r = 1, i = 1;

  while(i <= num)
         r *= i++;

  return r;
}