Control Structures in AP CSP: Making Algorithms Decide and Repeat

Boolean expression

An expression that evaluates to exactly one of two values: true or false; used to make decisions in control structures.

Relational (comparison) operator

An operator that compares two values and produces a Boolean result (true/false), such as =, ≠,

Logical operator

An operator that combines or modifies Boolean values, such as AND, OR, and NOT.

Equality operator (=) in AP CSP pseudocode

Tests whether two values are the same (e.g., x = 10).

Inequality operator (≠) in AP CSP pseudocode

Tests whether two values are different (e.g., answer ≠ "").

Less than (<) operator

True when the left value is smaller than the right value (e.g., score < 50).

Greater than (>) operator

True when the left value is larger than the right value (e.g., age > 13).

Less than or equal (≤) operator

True when the left value is smaller than or equal to the right value (e.g., temp ≤ 32).

Greater than or equal (≥) operator

True when the left value is larger than or equal to the right value (e.g., tries ≥ 3).

AND

A logical operator where A AND B is true only when both A and B are true.

OR (inclusive OR)

A logical operator where A OR B is true when at least one of A or B is true (including when both are true).

NOT

A logical operator that flips a Boolean value (NOT true → false; NOT false → true).

Selection

The control-flow idea that a program chooses which block of code to execute based on a Boolean expression (typically via conditionals).

Conditional

A control structure that chooses between different actions based on whether a Boolean expression is true or false.

IF statement (AP CSP)

Runs a block of statements only when its condition is true; if the condition is false, the block is skipped.

IF-ELSE statement (AP CSP)

Runs the IF block when the condition is true; otherwise runs the ELSE block, ensuring exactly one of the two blocks executes.

Compound condition

A Boolean expression that uses logical operators (AND/OR/NOT) to combine multiple comparisons into one decision.

Nested conditional

A conditional inside another conditional, used for multi-step decision-making where later tests depend on earlier outcomes.

Else-if chain (often represented by nesting)

A multi-way decision pattern that checks conditions in order so that at most one category/action is chosen.

Condition ordering (in nested conditionals)

The need to test more specific/higher-threshold conditions first so broader conditions don’t “catch” cases too early.

Iteration

Repeating a set of instructions multiple times; implemented using loops.

REPEAT n TIMES

A count-controlled loop that runs a fixed number of times when you know the number of repetitions in advance.

REPEAT UNTIL (condition)

A condition-controlled loop that repeats while the condition is false and stops when the condition becomes true.

FOR EACH item IN list

A list-traversal loop that processes every element of a list without manually managing an index.

Infinite loop

A loop that never stops, usually because the variables affecting the stopping condition never change inside the loop.