CAIE AS Level Computer Science (Paper 1) Revision Notes

Vocabulary flashcards covering fundamental computer science terms, definitions, hardware components, networking principles, and logic gate conventions from CAIE AS Level Computer Science Paper 1.

Denary

The base-10 number system using digits 0 to 9.

Binary

The base-2 number system using bits 0 and 1.

Hexadecimal

The base-16 number system using digits 0 to 9 and letters A to F (where A = 10, B = 11, C = 12, D = 13, E = 14, F = 15).

Binary Coded Decimal (BCD)

A number encoding scheme where each individual denary digit (0–9) is represented by its own 4-bit binary nibble.

Two's Complement

A binary representation technique used in computing for signed negative integers, obtained by adding 1 to the One’s Complement (flipped bits) of the number.

Pixel (Picture Element)

The smallest identifiable component of a bitmap image, defined by its position in the bitmap matrix and its colour.

Image Resolution

The number of pixels that make up a bitmap file, defined as the product of width and height in pixels (e.g. $1920 \times 1080$).

Screen Resolution

The number of horizontal and vertical pixels that a display screen can physically show.

Colour Depth (Bit Depth)

The number of bits used to represent the colour of a single pixel.

File Header

A set of bytes at the beginning of a bitmap file that stores metadata, including file type, image dimensions, colour depth, and compression details.

Lossless Compression

A compression technique that reduces file size without any loss of data, allowing the original file to be reconstructed when decompressed.

Run-Length Encoding (RLE)

A form of lossless compression that reduces sequences of adjacent, identical data items into a run count and a run value.

Client-Server Model

A network architecture where client devices request tasks, software, or data from a central dedicated server that manages shared resources and access.

DNS (Domain Name Service)

A hierarchical system of servers containing databases that translate human-readable domain names (URLs) into machine-readable IP addresses.

IPv4 Address

A 32-bit numerical identifier assigned to a network device, composed of four 8-bit octets represented in dotted decimal notation.

Network ID (netID)

The logical portion of an IP address that identifies the network to which the host belongs.

Host ID (hostID)

The logical portion of an IP address that identifies the individual device/workstation on a network.

CIDR (Classless Inter-Domain Routing)

An IP addressing notation that uses a suffix (e.g. /21) indicating how many bits are used for the netID, with the remaining bits allocated to host addresses.

Bridge

A hardware device that connects two LANs or LAN segments operating on the same protocol, filtering and forwarding data using MAC addresses.

Gateway

A network node that joins two dissimilar networks operating on different protocols, translating data packets between different protocol formats.

Input Device

Hardware equipment used to enter data or control signals into a computer system from the outside world.

Output Device

Hardware equipment used to display or present processed computer data in human-readable or physical forms.

Storage Device

Non-volatile hardware equipment used to retain data, software programs, and the operating system either temporarily or permanently.

Dynamic RAM (DRAM)

A type of volatile memory that stores each bit of data as an electrical charge in a cell consisting of a single transistor and capacitor, requiring continuous refreshing.

Static RAM (SRAM)

A type of volatile memory that uses flip-flops (multiple transistors per cell) to store data bits, requiring no refreshing while powered.

Logic Gate

A basic electronic component that takes one or more binary inputs and produces a single binary output according to a logical rule.

NOT Gate

A logic gate represented by $X = \text{NOT } A$ or $X = \overline{A}$ that inverts the binary input ($0 \rightarrow 1$, $1 \rightarrow 0$).

AND Gate

A logic gate represented by $X = A \text{ AND } B$ or $X = A \cdot B$, where the output is 1 only when both inputs are 1.

OR Gate

A logic gate represented by $X = A \text{ OR } B$ or $X = A + B$, where the output is 1 if at least one input is 1.

NAND Gate

A logic gate represented by $X = A \text{ NAND } B$ or $X = \overline{A \cdot B}$, where the output is 0 only when both inputs are 1.

NOR Gate

A logic gate represented by $X = A \text{ NOR } B$ or $X = \overline{A + B}$, where the output is 1 only when both inputs are 0.

XOR Gate

A logic gate represented by $X = A \text{ XOR } B$ or $X = A \oplus B$, where the output is 1 when inputs are different and 0 when both are identical.

Solid State Storage (Flash)

Storage devices, such as SSDs and USB drives, that use floating gate transistors (NAND flash memory) to trap electrons.

Magnetic Storage

Storage devices, such as Hard Disk Drives (HDD), that store data using spinning magnetisable platters and read/write heads.

Optical Storage

Storage media, such as CDs, DVDs, and Blu-ray discs, that encode data as lands and pits read by lasers.