Section 9.3 Relational and Equality Operators

We have already learned about several operators for numbers:

+, -, * addition, subtraction, and multiplication (integers and floats)
/ integer division for integers and floating point division for floats
% remainder (modulus) of an integer division

Next, we’ll learn about relational and equality operators that serve to compare the values of two quantities:

<, > less than and greater than operators
<=, >= less than or equal to, greater than or equal to
!= not equal to
== equal to (note the double equal sign; the single equal sign = has already been ’used up’ for our assignment operator)

Investigate 9.1.

Which of the following variables would C interpret as "true"? For example, if each variable was placed in the following code’s if statement as "variable", would the program output "True" or "False"?

```
int a = -1
```
🔗
```
char b = 'b'
```
🔗
```
float c = 0.0
```
🔗
```
int d = 4000
```
🔗

if (variable){
  printf("True")
}
else{
  printf("False")
}

A true logical relation evaluates to 1, whereas a false relation evaluates to 0. Examples:

Suppose x has the value 3.5. Then (x <= 5.0) evaluates to 1.
Suppose next that x has the value 7. Then (x <= 5.0) evaluates to 0.
(age == 30) evaluates to 1 if indeed age has the value 30, otherwise it evaluates to 0.

Note: Instead of (x <= 5.0) you could also write (5.0 >= x), and instead of (age == 30) you could just as well write (30 == age).

Investigate 9.2.

Does the following statement, which is comparing two characters, evaluate to true or false, according to C?

('A' > 'a')

Let’s look at an example.

If you cannot see this codecast, please click here.

Aside: Video Description.

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