C program to find hcf and lcm:

DESCRIPTION:
The code below finds highest common factor and least common
multiple of two integers. HCF is also known as
greatest common divisor(GCD) or greatest common factor(gcf).
CODE:
C programming code
#include <stdio.h>

int main() {
  int a, b, x, y, t, gcd, lcm;

  printf("Enter two integers\n");
  scanf("%d%d", &x, &y);

  a = x;
  b = y;

  while (b != 0) {
    t = b;
    b = a % b;
    a = t;
  }

  gcd = a;
  lcm = (x*y)/gcd;

  printf("Greatest common divisor of %d and %d = %d\n", x, y, gcd);
  printf("Least common multiple of %d and %d = %d\n", x, y, lcm);

  return 0;
}
C program to find hcf and lcm using recursion
#include <stdio.h>

long gcd(long, long);

int main() {
  long x, y, hcf, lcm;

  printf("Enter two integers\n");
  scanf("%ld%ld", &x, &y);

  hcf = gcd(x, y);
  lcm = (x*y)/hcf;

  printf("Greatest common divisor of %ld and %ld = %ld\n", x, y, hcf);
  printf("Least common multiple of %ld and %ld = %ld\n", x, y, lcm);

  return 0;
}

long gcd(long a, long b) {
  if (b == 0) {
    return a;
  }
  else {
    return gcd(b, a % b);
  }
}
C program to find hcf and lcm using function
#include <stdio.h>

long gcd(long, long);

int main() {
  long x, y, hcf, lcm;

  printf("Enter two integers\n");
  scanf("%ld%ld", &x, &y);

  hcf = gcd(x, y);
  lcm = (x*y)/hcf;

  printf("Greatest common divisor of %ld and %ld = %ld\n", x, y, hcf);
  printf("Least common multiple of %ld and %ld = %ld\n", x, y, lcm);

  return 0;
}

long gcd(long x, long y) {
  if (x == 0) {
    return y;
  }

  while (y != 0) {
    if (x > y) {
      x = x - y;
    }
    else {
      y = y - x;
    }
  }

  return x;
}
OUTPUT:
ENTER TWO INTEGERS:
9 15
GREATEST COMMON DIVISOR OF 9 AND 15= 3
LEAST COMMON MULTIPLE OF 9 AND 15=45