isPowerOfTwo.c

#include <stdio.h>

// fn to check if a number is a power of 2
int isPowerOfTwo(int n) {
    return n > 0 && !(n & (n - 1));
}

int main() {
    printf("How to find if a number is a power of 2\n");
    
    int testNumbers[] = {1, 2, 3, 4, 8, 16, 18, 32, 64, 100};
    int size = sizeof(testNumbers) / sizeof(testNumbers[0]);
    
    printf("Testing isPowerOfTwo fn :\n\n");
    for (int i = 0; i < size; i++) {
        int num = testNumbers[i];
        printf("%d is %sa power of `2`\n", num, isPowerOfTwo(num) ? "" : "not ");
    }
    
    return 0;
}

Test it here: https://www.programiz.com/online-compiler/6BTnyB8EfFwvZ