Read a number and write whether it is negative or positive or zero

This is the simplest solution:

#include <stdio.h>
int main(void)
{
        int n;
        printf("Enter a number\n");
        scanf("%d", &n);
        if(n > 0)
                printf("Positive\n");
        else if(n < 0)
                printf("Negative\n");
        else
                printf("Zero\n");
        return 0;
}

It works fine if I enter correct numbers, but if I enter text instead of a number, it says it's a positive number. This is because scanf() doesn't do a "strict" check, so we have to add it ourselves!

Later, we'll see how to add more stringent checks to scanf()'s reading.