Newton's Binomial Theorem

I stumbled upon this formula in a book the other day and set about coding it in C from scratch. At the end of the day any summation can be easily turned into a for loop.

I also wrote my own functions for exponential, combinatorial numbers and factorial.

#include <stdio.h>

#define A 5

#define B 3

#define EXPN 7

int myexp(int base, int expn){

    int res=1; int i=0;

    if ((base == 0) && (expn == 0)) return 1;

      

    for (i=0;i<expn;i++){

      res=res*base;

    }

    return res;

}

int fact(int num){

  int i=0, res=num;

  

  if ((num == 0)) return 1;

  for (i=1; i<num;i++){

  res = res * (num-i);

  }

 return res;

}

int comb(int m, int n){

int res=0;

  if ((n == 0)) return 1;

  res=(fact(m) / (fact(n) * fact(m-n)));

  return res;

}

int binomial (int a, int b, int expn){

int k=0, res=0, combr=0;

  for (k=0;k<=expn;k++){

      combr = comb(expn,k);

      res = res + (combr * myexp(a,expn-k)*myexp(b,k));

  }

  return res;

}

void pretty(int expn){

    int i=0;

    for (i=0; i<expn; i++){

    printf("%d*a^%d * b^%d +\n",comb(expn,i),expn-i, i);

    }

    printf("%d*a^%d * b^%d\n",comb(expn,i),expn-i, i);

}

int main(){

   //printf("%d\n", comb(7,0));

   pretty(EXPN);

   printf("For a=%d and b=%d and exp=%d the result is...%d\n",A,B,EXPN, binomial(A,B,EXPN));

}