Cameroon GCE A Level ICT flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Data

Raw, unprocessed facts, symbols or signals with no context, such as a list of numbers or characters, which on their own do not convey meaning to a user.

Information

Data that has been processed, organised and given context so that it has meaning and can support decisions, for example totals, averages or formatted reports.

Bit and byte

A bit is a single binary digit, 0 or 1. A byte is a group of eight bits and is the standard unit for storing one character code.

Binary prefix conversion

Using powers of two: 1 KiB equals 1024 bytes, 1 MiB equals 1024 KiB, 1 GiB equals 1024 MiB. Decimal prefixes use powers of ten instead.

Hexadecimal

A base-16 number system using digits 0-9 and letters A-F. Each hex digit represents exactly four binary bits, making it a compact notation for memory addresses and colour codes.

Two's complement

A signed binary representation in which a negative number is formed by inverting all bits of its positive form and adding one. It allows subtraction using addition circuits.

ASCII

American Standard Code for Information Interchange, a 7-bit character code giving 128 codes for letters, digits, punctuation and control characters. Extended versions use 8 bits.

Unicode

A character encoding standard covering the scripts of the world. Its UTF-8 form uses one to four bytes per character and remains compatible with ASCII for basic Latin text.

Von Neumann architecture

A computer design in which instructions and data share the same main memory and travel over common buses to the CPU, which fetches, decodes and executes instructions sequentially.

Fetch-decode-execute cycle

The repeated CPU operation: fetch the instruction addressed by the program counter, decode it in the control unit, execute it in the ALU, store the result and increment the counter.

Cache memory

Fast, small, volatile memory between the CPU and main memory that holds recently or frequently used instructions and data, reducing average access time. L1 is fastest and smallest.

RAM versus ROM

RAM is volatile read/write main memory holding programs and data in use. ROM is non-volatile and normally read-only, holding firmware such as the bootstrap loader.

Solid-state storage

Non-volatile flash memory with no moving parts, giving fast random access, low power use and shock resistance, but higher cost per gigabyte and limited write cycles compared with magnetic disks.

Operating system

System software that manages hardware and provides services: process scheduling, memory allocation, file management, input/output control, user interface and basic security.

Compiler versus interpreter

A compiler translates the whole source program to object code before running and lists all errors at the end. An interpreter translates and runs line by line, stopping at the first error.

Iteration

A programming construct that repeats a block of statements, either a counted loop (FOR) with a known number of repetitions or a conditional loop (WHILE, REPEAT) controlled by a test.

Parameter passing

Supplying values, called arguments, to a procedure or function so it can operate on different data. By value passes a copy; by reference passes access to the original variable.

Algorithm

A finite, unambiguous sequence of steps that takes input, performs processing and terminates with a result. It can be expressed as pseudocode, a flowchart or program code.

Primary key

A field or combination of fields that uniquely identifies each record in a table. It cannot be null and must be unique, and it links to foreign keys in other tables.

Third normal form

A table is in 3NF when it is in 2NF and contains no transitive dependencies, meaning non-key fields depend only on the primary key and not on other non-key fields.

SQL SELECT

The query statement that retrieves data: SELECT chooses fields, FROM names the table, WHERE filters rows, GROUP BY aggregates and ORDER BY sorts the result set.

Star topology

A network layout where every device connects to a central hub or switch. Failure of one cable affects one device, but failure of the centre disables the whole network.

LAN versus WAN

A LAN covers a small area such as one building and is usually privately owned. A WAN spans large distances and often uses leased telecommunications links or public infrastructure.

MAC address

A unique hardware identifier burned into a network interface card, usually 48 bits written as six hexadecimal pairs. It works at the data link layer of the OSI model.

DNS

The Domain Name System translates human-readable domain names into IP addresses, using a distributed hierarchy of name servers so users need not remember numeric addresses.

TCP versus UDP

TCP is connection-oriented, acknowledges packets and retransmits lost ones, suiting file transfer. UDP is connectionless with less overhead, suiting streaming and voice where speed matters more than perfection.

OSI reference model

A seven-layer conceptual model: physical, data link, network, transport, session, presentation and application. Each layer provides services to the layer above and hides lower-level detail.

Computer virus

Malicious code that attaches itself to a host file or program and spreads when that host is executed, often damaging data or disrupting normal operation of the system.

Phishing

A social-engineering attack using fraudulent emails, messages or websites that impersonate a trusted organisation to trick users into revealing passwords, card numbers or other credentials.

Symmetric encryption

Encryption using a single shared secret key for both encryption and decryption. It is fast and suits bulk data, but the key must be distributed securely to both parties.

Digital signature

A value created by encrypting a hash of a message with the sender's private key. It proves authenticity and integrity and provides non-repudiation when checked with the public key.

Validation versus verification

Validation checks that input is reasonable and within rules such as range, type, presence or format. Verification checks that data was copied or entered accurately, for example by double entry.

System development life cycle

The staged process of building an information system: requirements analysis, design, implementation, testing, deployment and maintenance, carried out sequentially or iteratively.