Relational Operators

Relational operators can be used to determine the relationship between two variables, returning True or False dependant on the relationship.

Operator Description
< less than
> more than
<= less than or equal to
>= greater than or equal to
== equals
!= not equal to

Conditional Statements

Conditional statements operate on a condition, and are more broadly known as 'if/while' statements. These conditions rely on relational operators.
Similar to Javascript, C's conditional statements are enclosed in brackets.

'if' statements

#include <stdio.h> 

int main(void){
	int myint;
	scanf("%d", &myint);
	if (myint > 5){ // conditional
		printf("More than five!");
	} else {
		printf("Less than five!");
	}
}

Note that else statements directly following the closing parentheses of the if statement, and contain parentheses of their own. This too happens with else if (which cannot be last).

As (myint > 5) does not take into account whether myint is equal to 5, an else if statement can be used to distinguish between less than, more than and equal to five.

#include <stdio.h> 

int main(void){
	int myint;
	scanf("%d", &myint);
	if (myint > 5){
		printf("More than five!");
	} else if (myint < 5) {
		printf("Less than five!");
	} else {
        printf("Five!");
    }
}

Code in this else if will only run if the previous statements evaluate to False (again, 0 in C). Code in the else will only run if all other conditions evaluate to False.

'while' statements

While statements run for the duration that something is True.

Logical Operators

Logical operators can be used to 'chain' conditions.

Operator Meaning Description
&& AND Returns True if both conditions are true.
|| OR Returns True if any condition is true.
! NOT Reverses the expression.

Related Notes