AP®Computer ScienceCollege BoardComputer Science PrinciplesRevision NotesUnit 3: Algorithms and ProgrammingBoolean ExpressionsBoolean Expressions & Operators

Boolean Expressions & Operators (College Board AP® Computer Science Principles): Revision Note

Written by: Robert Hampton

Reviewed by: James Woodhouse

Updated on 24 March 2026

Boolean values & comparisons

What is a Boolean value?

A Boolean value is a data type that can only be true or false
Booleans are fundamental to decision-making in programs: conditions are evaluated to produce a Boolean result
Relational operators compare two values and return a Boolean result

Operator	Meaning	Example	Result
`=`	Equal to	`5 = 5`	`true`
`≠`	Not equal to	`5 ≠ 3`	`true`
`<`	Less than	`3 < 5`	`true`
`>`	Greater than	`5 > 8`	`false`
`≤`	Less than or equal to	`5 ≤ 5`	`true`
`≥`	Greater than or equal to	`3 ≥ 5`	`false`

Boolean operands

Boolean operands are the values passed into a Boolean operation and can be:
- Literal Boolean values (true or false)
- Variables that hold Boolean values (isLoggedIn, isPassing)
- Relational expressions that evaluate to a Boolean (score ≥ 50)
Comparison expressions evaluate to true or false before being used in a conditional or logic statement

Boolean logic operators

How are Boolean expressions combined?

Logic operators allow Boolean values to be combined to form more complex conditions
AP CSP pseudocode uses three logic operators: NOT, AND, and OR

Operator	Description	Example	Result
`NOT`	Reverses a Boolean value	`NOT true`	`false`
`AND`	Returns `true` only if both operands are `true`	`true AND false`	`false`
`OR`	Returns `true` if at least one operand is `true`	`true OR false`	`true`

Logic operators in practice

score ← 72
isPassing ← score ≥ 50
isHonors ← score ≥ 90
DISPLAY(isPassing AND NOT isHonors)

isPassing is true (72 ≥ 50), isHonors is false (72 < 90), NOT isHonors is true
true AND true evaluates to true, so the program displays true

Truth tables

A truth table shows every possible combination of Boolean inputs and the corresponding output for each logic operator

A	B	A AND B	A OR B
`true`	`true`	`true`	`true`
`true`	`false`	`false`	`true`
`false`	`true`	`false`	`true`
`false`	`false`	`false`	`false`

A	NOT A
`true`	`false`
`false`	`true`

Examiner Tips and Tricks

AND requires both conditions to be true — if either is false, the whole expression is false. OR only returns false when both conditions are false. When evaluating complex Boolean expressions, simplify one operator at a time from the inside out.
For the AP Create Performance Task, Boolean expressions drive the conditionals and loops your program must include — be prepared to explain how a condition in your code determines program behavior.

Worked Example

What is the value of the following expression?

NOT (3 > 5) AND (4 = 4)

(A) true

(B) false

(C) 3

(D) 4

[1]

Answer:

(A) true [1 mark]

NOT (3 > 5) evaluates to NOT false = true, and 4 = 4 is true, so true AND true evaluates to true

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

I would just like to say a massive thank you for putting together such a brilliant, easy to use website.I really think using this site helped me secure my top gradesin science and maths. You really did save my exams! Thank you.

Beth
IGCSE Student

This website is soooo useful and I can’t ever thank you enough for organising questions by topic like this. Furthermore, the name of the website could not have been more appropriate as it literally did SAVE MY EXAMS!

Fathima
A Level Student

Incredible! SO worth my money, the revision notes have everything I need to know and are so easy to understand. I actually enjoy revising! It makes me feel a lot more confident for my GCSEs in a few months.

Kate
GCSE Student

Absolutely brilliant, both my girls used it for A levels and GCSE. It's saves on paper copies, also beneficial exam questions ranked from easy to hard. It's removed a lot of stress from the exams.

Sameera
Parent

Just to say that your resources are the best I have seen and I have been teaching chemistry at different levels for about 40 years

Mark
Chemistry Teacher

Excellent