&& condition working as || in do while loop in c

Question

The AND (&&) condition evaluates as OR(||) in this code. For ex., when user inputs numbers 6 and 7, the output is 12 but when the I replace && with || the output is 42.

#include<stdio.h>

int main()
{
    int a,b,max,lcm;

    printf("Enter 2 numbers: ");
    scanf("%d %d", &a, &b);

    if(a>b)
    {
        max=a;
    }
    else
    {
        max=b;  
    }

    do
    {
        max++;
    } while(max%a!=0 && max%b!=0);

    lcm=max;
    printf("LCM of %d and %d is %d\n", a,b,lcm);

    return 0;
}

Answer 1

No, the && condition is working as an and condition, just as it should. When you input 6 and 7, max%a evaluates to 0 when max is 12. At that point max%a != 0 evaluates to false (false && true == false), and max%a != 0 && max%b != 0 evaluates to false, and your loop exits. However, max%a != 0 || max%b != 0 evaluates to true (max%b is 5 for a max of 12 and b of 7, false || true == true), so the loop continues.