Computer Science Definitions and Concepts

Comprehensive vocabulary flashcards covering fundamental Computer Science topics including programming constructs, data structures, algorithms, databases, validation, verification, and digital logic.

Program

A list of instructions that does a specific task, which can be written in a high-level language or low-level language.

Pseudocode

A method that uses English words and mathematical notations to design the steps of a program.

Flowchart

A diagram that designs the steps of a program by using a standard set of symbols joined by lines to show the direction of flow.

Trace Table

A table used to record the results from each step in an algorithm, track the value of a variable each time it changes, and document the dry run of a program.

Tracing (Dry Run)

The manual exercise of working through an algorithm step by step.

Variable

A named data store that contains a value that can change during the execution of a program.

Constant

A named data store that contains a value that does not change during the execution of a program.

Comments

Blocks of text in pseudocode that are not executed, used to explain the purpose of each section of code.

Top-Down Design

The breaking down of a computer system into a set of subsystems, and then breaking each subsystem into smaller ones until each subsystem performs a single action.

Stepwise Refinement

The process of breaking down a system into smaller subsystems.

Module

An individual section of code that can be used by other programs.

Structure Chart

A diagram that shows the design of a computer system in a hierarchical way, with each level giving a more detailed breakdown of the system.

Abstraction

Simplifying a problem by selecting required elements and filtering out irrelevant characteristics from those elements.

Decomposition

Breaking down a complex problem into smaller parts which can then be divided into even smaller parts that can be solved easily.

Iterative Testing

The process where tests are conducted on each subsystem of a program, errors are corrected, and tests are repeated until the subsystem performs as required.

Arithmetic Operators

Operators used to perform calculations, such as $+$, $-$, $*$, $/$, and $^{\wedge}$.

Relational Operators

Operators used in comparisons and conditional (selection) statements, including $>$, $>=$, $<$, $<=$, $=$, and $<>$.

Logical Operators

Operators used for operations with true or false values to form a more complex expression, such as AND, OR, and NOT.

Integer

A data type consisting of a positive or negative whole number that can be used in mathematical operations.

Real

A data type consisting of a positive or negative number with a fractional part that can be used in mathematical operations.

Char

A data type representing a single character from the keyboard.

String

A data type consisting of a sequence of characters.

Boolean

A data type consisting of data with two possible values, TRUE or FALSE.

Assignment Statement

A statement that changes the value of a variable or an element in an array.

Prompt Message

An output message displayed before user input stating the input required, helping the user know what they are expected to enter.

FOR .. TO .. NEXT

A count-controlled loop structure that iterates a set (known) number of times.

WHILE .. DO .. ENDWHILE

A pre-condition loop that iterates whilst a specified condition exists, where criteria is checked at the start and the loop may never run.

REPEAT .. UNTIL

A post-condition loop that iterates until a condition is met, where criteria is tested at the end and the loop iterates at least once.

Totalling

The process of summing a list of numbers.

Counting

The process of finding how many items are in a list.

Array

A data structure that holds a number of elements of the same data type under a single identifier.

Index

The position of an element in an array.

Dimension

The number of indexes required to access an element in an array.

One-dimensional (1-D) Array

A list or single column of items of the same data type stored under a single name, with a single index to identify each element.

Two-dimensional (2-D) Array

A table-like collection of items of the same data type with rows and columns, stored under a single name with two indexes to identify each element.

Linear Search

The process of finding a value within a list of elements by looping from the first element to the last and comparing each element with the search value.

Bubble Sort

The process of sorting a list of items alphabetically or numerically by repeatedly comparing adjacent elements and swapping them if they are in the wrong order.

Subroutine

A named sub-program written in a high-level language to perform a frequently used operation, which can be called when needed and reused.

Function

A subroutine that always returns a value to the main program.

Procedure

A subroutine that does not return a value.

Local Variable

A variable defined inside the scope of a subroutine whose scope is restricted to that defined block of code and cannot be accessed elsewhere.

Global Variable

A variable defined outside the scope of any subroutine whose scope covers the whole program and can be accessed and modified anywhere.

Parameter

A variable used to pass values from the main program to a subroutine (procedure or function).

Library Routine

A pre-tested list of programming instructions that is given a name and is already available for use.

DIV

An operator used to perform integer division of two numbers with the fractional part discarded.

MOD

An operator used to perform division when one number is divided by another and find the remainder.

Database

A structured collection of related data that allows people to extract information in a way that meets their needs.

Primary Key

A field that contains unique data and cannot have duplicates.

Validation

The automated checking by a program that data to be entered is sensible.

Type Check

A validation check that ensures data entered has the appropriate data type.

Presence Check

A validation check that ensures some data has been entered and the value has not been left blank.

Range Check

A validation check that ensures only numbers within a specified range are accepted.

Length Check

A validation check that ensures data contains an exact number of characters.

Format Check

A validation check that ensures characters entered conform to a pre-defined pattern.

Check Digit

A digit calculated from all other digits and appended to a number, commonly used in barcodes.

Verification

Checking that data has not changed during input to a computer or during transfer between computers.

Screen/Visual Check

A verification method where entered data is visually compared with the source document by a user to confirm they match.

Double Data Entry

A verification method where data is entered twice (often by different people) and the computer checks that both entries are equal.

Normal Data

Correct test data within the range of acceptability that should be accepted by the program.

Abnormal Data

Test data outside the limits of acceptability or of the wrong data type, which should be rejected.

Extreme Data

Test data consisting of the largest or smallest acceptable value that should still be accepted.

Boundary Data

Test data consisting of the largest or smallest acceptable value and the corresponding smallest or largest rejected value.

Logic Gate

A small physical device that controls the flow of electrical signals in a pre-determined way to carry out a logical operation.

Logic Circuit

A combination of logic gates connected together to carry out a particular function.

Truth Table

A table used to show the inputs and output of a Boolean expression, logic gate, or logic circuit considering all possible combinations of 0s and 1s.