Relational and Equality Operators

Section 9.3 Relational and Equality Operators

We have already learned about several operators for numbers:

+, -, * addition, subtraction, and multiplication (integers and floats)

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/ integer division for integers and floating point division for floats

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% remainder (modulus) of an integer division

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

<, > less than and greater than operators

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<=, >= less than or equal to, greater than or equal to

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!= not equal to

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== equal to (note the double equal sign; the single equal sign = has already been ’used up’ for our assignment operator)

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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"?

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```
int a = -1
```
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```
char b = 'b'
```
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```
float c = 0.0
```
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```
int d = 4000
```
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if (variable){
  printf("True")
}
else{
  printf("False")
}

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

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Suppose x has the value 3.5. Then (x <= 5.0) evaluates to 1.

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Suppose next that x has the value 7. Then (x <= 5.0) evaluates to 0.

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(age == 30) evaluates to 1 if indeed age has the value 30, otherwise it evaluates to 0.

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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).

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Investigate 9.2.

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

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('A' > 'a')

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Let’s look at an example.

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If you cannot see this codecast, please click here.

Check Your Understanding Check Your Understanding

1.

You are writing a C program that calculates the price of a rental car, depending on how many miles the user wants to drive. If the user drives less than 50 miles then the price of the car is a flat fee of $40. If on the other hand the user drives 50 or more miles, then the cost is computed as $0.70 per mile plus a handling fee of $5.

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Please complete the following C program: After the user has entered the number of miles they wish to drive, the program should output the price of the rental car in dollars (with two decimal places).

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admin.....open in new window

When your program performs correctly you’ll be given a keyword to enter in Canvas.

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