IGCSE Computer Science Paper 2 Notes

Comprehensive vocabulary flashcards covering the Program Development Life Cycle, validation, verification, test data types, program structures, and library routines based on the IGCSE Computer Science Paper 2 notes.

Analysis Stage

The stage of the Program Development Life Cycle used to precisely understand the problem the program has to solve.

Abstraction

A process of simplifying a problem by removing unnecessary details and filtering out irrelevant characteristics to focus on identification of the solution.

Decomposition

Breaking down a large problem into smaller, more understandable and manageable parts that can be solved and tested independently.

Inputs

Data entered into the system.

Outputs

Data that is produced by the system and displayed to the user.

Processes

Subroutines and algorithms that turn input and stored data into output.

Storage

Data that is stored on a physical device in RAM while the program is running.

Design Stage

The construction of a solution using standard methods like flowcharts, pseudocode, and structure diagrams.

Structure Diagrams

A hierarchical diagram showing the breakdown of a computer program into sub-programs.

Flowcharts

A diagram showing the ordered steps to complete a computer program.

Pseudocode

A text-based tool showing what a program does in plain language (English words/statements) to describe an algorithm.

Coding Stage

The stage where the program is written using a programming language, followed by iterative testing.

Testing Stage

The stage where a program is tested for errors using multiple sets of test data to ensure it meets requirements.

Validation

An automated check carried out by a computer to ensure that the data entered is reasonable, sensible, and meaningful/acceptable.

Range Check

A validation check that ensures data entered is within a particular range or fits within specific values.

Length Check

A validation check that checks the length of a string.

Type Check

A validation check that checks the data type of a field.

Presence Check

A validation check that checks if any data has been entered in a field.

Format Check

A validation check that ensures data entered is in the correct format, such as $\text{dd/mm/yyyy}$.

Check Digit

A data entry check calculated using an algorithm and then attached to a code.

Verification

A process that ensures data has been accurately copied from one source to another and tests if data input is the same as the data intended to be input.

Double-entry check

A verification method where data is entered twice and the two entries are compared for matches.

Visual check

A verification method where a user looks through data entered by eye and confirms no changes were made during entry.

Normal data

A test data value that is accepted.

Abnormal data

A test data value that is rejected.

Extreme data

The largest and smallest acceptable values.

Boundary data

The largest/smallest acceptable values along with their corresponding largest/smallest rejected values.

Sequence

Lines of code which are run one line at a time in order, crucial to the flow of a program.

Selection

When the flow of a program is changed depending on a set of conditions, using structures like IF… THEN… ELSE or CASE OF… OTHERWISE.

Iteration

The repetition of a line or block of code using a loop.

Count-Controlled Loop (FOR Loop)

A loop where the number of iterations is pre-determined and the code is repeated a fixed number of times.

Pre-conditioned Loop (WHILE Loop)

A loop where the condition is checked before the loop is run; statements only execute if the expression evaluates to TRUE.

Post-conditioned Loop (REPEAT Loop)

A loop where conditions are checked at the end, meaning the loop runs at least $1$ time.

Variables

Identifiers used to store data and values that can change during the execution of a program.

Constants

Identifiers used to store data and values that are never changed during program execution.

Parameters

Values used to pass data from the main program to a function or procedure so they can be re-used with different data.

Functions and Procedures

Blocks of code that divide a program into manageable segments under a single identifier, making programs easier to maintain, read, and debug.

Local variables

Variables whose scope is a defined block of code and whose value cannot be changed elsewhere in the program.

Global variables

Variables whose scope is the whole program and whose value can be changed anywhere.

MOD

A library routine that returns the remainder when an integer division is performed, e.g., $MOD(7,2) = 1$.

DIV

A library routine that performs integer division, returning only the whole number part of the answer, e.g., $DIV(9,4) = 2$.

ROUND

A library routine that returns a value rounded to a specific number of digits or decimal places, based on whether the preceding digit is $\ge 5$ or $< 5$.

RANDOM

A library routine used to generate and return pseudo random numbers, usually within a specified range.

SQL SELECT

The SQL command that lists the fields to be displayed.

SQL FROM

The SQL command that identifies the table from which to retrieve data.

SQL WHERE

The SQL command that identifies the search criteria for the data.