Cambridge IGCSE Computer Science: Data Representation and Software Development

Vocabulary practice flashcards covering software development life cycle stages, binary and hexadecimal arithmetic, binary shifts, two's complement, ASCII, Unicode, digital sound sampling, bitmap image representation, and data compression techniques.

Waterfall development

A linear software development methodology where progress flows sequentially through distinct stages: Analysis, Design, Coding, and Testing.

Analysis stage

The initial stage of the software life cycle that involves examining the problem computationally, employing abstraction and decomposition to identify the core problem and establish user requirements.

Requirements specification

A formal document created after decomposing a problem that outlines the necessary features, inputs, outputs, and constraints the software must fulfill.

Problem decomposition

The process of breaking down a complex problem into smaller, solvable parts from the client's perspective, identifying each part that needs solving rather than how it will be coded.

Abstraction

The computational thinking technique of removing unnecessary details from a problem to concentrate solely on the essential components needed to solve it.

Design stage

The life cycle stage that takes the requirements from the analysis stage and determines how the software will be constructed, including the overall program structure, algorithms, inputs, processes, outputs, and storage.

Structure diagram

A hierarchical design diagram using boxes and branches to graphically show how a system is repeatedly decomposed into smaller, manageable sub-systems.

Pseudocode

A language-independent method of writing out algorithms that resembles programming code and is easy for programmers to read regardless of the programming language they use.

Iterative testing

Testing conducted continuously throughout the coding stage, where the program is checked and verified after each iteration when a new feature is added or an error is fixed.

Testing stage

The final stage of the development life cycle where a completed program is executed with planned test data to verify that the actual output matches expected results.

Hexadecimal

A base-$16$ numbering system that utilizes the digits $0\text{--}9$ and letters $\text{A}\text{--}\text{F}$ to represent binary data in a compact, human-readable format.

Nibble

A group of $4\,\text{bits}$ of binary data, equivalent to exactly one hexadecimal digit.

Overflow error

An error that occurs when the numerical result of a binary addition is too large to be stored within the fixed register size or number of bits allocated by the computer architecture (e.g., exceeding $255$ in an $8\,\text{bit}$ register).

Logical left shift

A bitwise operation that shifts all bits in a binary number to the left and inserts zeros into the vacated least significant bits, effectively multiplying the number by $2$ for each place shifted.

Logical right shift

A bitwise operation that shifts all bits in a binary number to the right and inserts zeros into the vacated most significant bits, effectively dividing the number by $2$ and discarding any fractional remainder.

Loss of precision

The permanent loss of fractional data that occurs during a logical right shift when $1\,\text{bits}$ are shifted out beyond the least significant bit.

Two's complement

A method used to represent positive and negative binary integers where the most significant bit carries a negative weight (such as $-128$ in an $8\,\text{bit}$ number); negative values are derived by inverting all bits of the positive equivalent and adding $1$.

Character set

A defined collection of characters, digits, symbols, and control codes that can be recognized, processed, and represented in binary by a computer system.

ASCII

American Standard Code for Information Interchange; a 7-bit character encoding system that represents $128$ characters, including uppercase and lowercase English letters, numbers $0\text{--}9$, punctuation symbols, and control codes.

Extended ASCII

An 8-bit character encoding system that expands the standard character set to encode up to $256$ characters ($2^8$), accommodating additional symbols, accents, and non-English characters.

Unicode

A universal character encoding standard using 16-bit ($65{,}536$ characters) or 32-bit (over $4\,\text{billion}$ characters) representations to support global alphabets, diverse scripts, and emojis.

Concatenation

The programming operation of linking two or more strings together end-to-end, commonly executed using the $+$ operator.

Analogue sound

Continuous acoustic sound signals characterized by smooth, unbroken waves.

Digital sound

Discrete, non-continuous sound data created by repeatedly measuring, recording, and storing the amplitude values of an analogue wave as binary numbers.

Analogue to Digital Convertor (ADC)

A hardware device that converts continuous analogue audio signals into discrete digital binary data for processing and storage by a computer.

Digital to Audio Convertor (DAC)

A hardware device that converts discrete digital binary audio data back into continuous analogue sound waves for output through speakers or headphones.

Sample rate

The frequency at which amplitude measurements of an analogue sound wave are taken per second, measured in hertz ($\text{Hz}$).

Sample resolution

Also called audio bit depth; the number of bits allocated to store each individual amplitude measurement of a sound sample.

Bitmap image

A digital graphic format (also called a raster image) composed of a two-dimensional grid of picture elements called pixels.

Pixel

Short for picture element; the smallest identifiable, single-coloured unit in a bitmap graphic, represented by a binary value.

Image resolution

The total number of pixels comprising a digital image, calculated by multiplying the image width by its height in pixels.

Colour depth

The number of bits ($n$) allocated per pixel in an image, determining the total variety of available colours ($2^n$) that can be represented.

RGB colour model

An additive colour system where each pixel's colour is defined by varying intensities of red, green, and blue light, typically requiring $8\,\text{bits}$ per colour channel ($0\text{--}255$) and $24\,\text{bits}$ per pixel ($16.7\,\text{million}$ colours).

PBM (Portable Bitmap)

A simple monochrome image file format that records image dimensions and represents black and white pixels directly with $1\,\text{s}$ and $0\,\text{s}$.

Data compression

The application of algorithms to reduce the total number of bits required to represent data, decreasing storage requirements, reducing bandwidth consumption, and speeding up network transmission.

Decompression

The process of restoring compressed data back into its original or usable format for display, playback, or execution.

Lossy compression

A compression technique that permanently removes unnecessary or less perceptible data from files (e.g., JPEG, MP3, MP4), reducing file size significantly at the expense of original quality.

Lossless compression

A compression technique that reduces file size without discarding any data (e.g., PNG, ZIP, GIF, FLAC), allowing the original file to be reconstructed perfectly upon decompression.

Digital artefacts

Unintended visual imperfections, noise, or pixel blocks appearing in images and videos as a result of permanent data loss caused by lossy compression.

Run Length Encoding (RLE)

A lossless compression algorithm that identifies consecutive sequences of identical data values and encodes them as frequency/data pairs.

Buffering

The process of preloading a segment of streaming audio or video data into temporary memory before playback begins to prevent pauses or playback interruptions caused by network latency.