Boolean Operators

Sometimes we want to check multiple conditions at once, effectively saying things like "if something and something", or "if something or something". C has the following operators to do that:

• && means and: the value of a && b is true if both a and b are true;
• || means or: the value of a || b is true if either a, or b, or both of them are true;
• ! means not: the value of !a is true if a is false.

Note that they are && and ||, but not & and |. To make things more confusing, & and | are valid operators too – they are called bitwise operators and do something completely different, which we'll discuss later. So just make sure to only use && and || for now.

Let's write some code. How about, maybe, a function which checks that the given number x is between two other numbers a and b (inclusive)?

#include <stdio.h>

int is_between(int x, int a, int b) {
	/* write the code! remember: 0 is false, everything else is true */
	return 0;
}

int main() {
	printf("is 1 between 3 and 7? %d\n", is_between(1, 3, 7));
	printf("is 3 between 3 and 7? %d\n", is_between(3, 3, 7));
	printf("is 5 between 3 and 7? %d\n", is_between(5, 3, 7));
	printf("is 7 between 3 and 7? %d\n", is_between(7, 3, 7));
	printf("is 9 between 3 and 7? %d\n", is_between(9, 3, 7));
	return 0;
}