Big Idea 3: Algorithms and Programming

Vocabulary terms and definitions from the Algorithms and Programming lecture notes based on the AP Computer Science Principles curriculum.

algorithm

A finite set of instructions that accomplishes a specific task. Every algorithm can be constructed using combinations of sequencing, selection, and iteration.

API

A specification that defines how procedures in a library behave and how to use them, without requiring knowledge of how they are implemented.

argument

The value passed to a parameter when a procedure is called.

assignment

The process of storing a value in a variable.

Binary search

A search algorithm that starts at the middle of a sorted data set and eliminates half of the remaining elements with each step. Requires data to be in sorted order.

Boolean value

A value that is either true or false.

Conditional statement

An IF or IF/ELSE statement that affects the sequential flow of control by executing different statements based on the value of a Boolean expression.

Data abstraction

Using a list (or other collection type) to store multiple elements in a single structure, allowing program code to manage complexity by representing multiple related values under one variable.

element

An individual value within a list, accessed by its index position.

heuristic

An approach to a problem that finds a good solution in reasonable time, but does not guarantee the best or correct solution.

index

The position of an element in a list. AP pseudocode uses index values from $1$ through the number of elements in the list.

Iteration

A repetitive portion of an algorithm. Iteration repeats until a given condition is met or for a specified number of times. Recursion is also a form of iteration.

library

A set of procedures that have been written and tested and are available for use in building programs.

List traversal

Iterating over all elements of a list, accessing each element one at a time, commonly used to search, modify, or compute with list values.

Relational operators

Operators that combine Boolean values: AND (true if both are true), OR (true if at least one is true), NOT (negates a Boolean value).

moduarity

The subdivision of a computer program into separate subprograms, achieved through procedural abstraction.

Nested conditional

A conditional statement that exists within another conditional statement.

parameter

A variable in the definition of a procedure that allows the procedure to receive input values when it is called.

Procedural extraction

A type of abstraction that provides a name for a process and allows a procedure to be used knowing only what it does, not how it does it.

procedures

A named group of programming instructions that may have parameters and return values. Also called functions, methods, or subroutines depending on the language.

pseudocode

A way of expressing an algorithm using natural language or informal notation, without the syntax of a specific programming language.

Logistical operators

Operators that compare two values and evaluate to a Boolean: equal ($=$), not equal ($\neq$), less than ($<$), greater than ($>$), less than or equal to ($\le$), greater than or equal to ($\ge$).

Return value

The value a procedure sends back to the code that called it.

selection

A programming construct that determines which parts of an algorithm are executed based on a condition being true or false.

sequencing

The application of each step of an algorithm in the order in which the code statements are given.

Sequential search

A search algorithm that checks each element of a list one by one until the target value is found or all elements have been checked.

Simulation

An abstraction of a more complex object or phenomenon for a specific purpose. Simulations mimic real-world events to allow investigation without real-world constraints.

string

An ordered sequence of characters used to represent text.

Undecidable problem

A problem for which no algorithm can be constructed that always produces a correct yes or no answer for every possible input.

variable

An abstraction inside a program that can hold a value. Each variable has associated data storage that represents one value at a time, but that value can be a list or other collection containing multiple values.