Fiches Informatique GCSE : 56 termes clés, pour Brainlag Flashcards et Anki

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Chaque réponse reprend mot pour mot une leçon gratuite de Brainlag Learn, où l'idée est expliquée en entier. Les organismes d'examen formulent certaines définitions autrement : compare avec ton programme.

Abstraction

Remove the details that do not matter, so you can focus on the ones that do.

Decomposition

Break a big problem into smaller problems that are each easier to solve.

Algorithmic thinking

Work out the exact steps, in order, that solve the problem.

Algorithm

A sequence of steps that solves a problem.

Structure diagram

The whole problem in the top box, its subsections in a row below, and the smaller tasks of each subsection below that.

Linear search

Starts at the first item and checks each one in turn until it finds what it is looking for, or runs out of items.

Binary search

Compares the target with the middle item, then throws away the half that cannot hold it.

AND gate

1 only when both inputs are 1.

OR gate

1 when at least one input is 1.

XOR gate

1 when the inputs are different.

NOT gate

One input, flipped.

CPU

Fetches and carries out instructions.

ALU

Does calculations and comparisons.

Control unit

Decodes instructions and sends signals to make the other parts act, in step with the clock.

Cache

A small amount of very fast memory on or near the CPU.

Registers

Tiny, very fast stores inside the CPU, each with one job.

Von Neumann architecture

Program instructions and data are stored together in the same main memory, and the CPU fetches them one at a time.

Clock speed

Cycles per second, in hertz.

Cores

Each core is a separate processor.

Embedded system

A computer built into a larger device to do one dedicated job

Hexadecimal

(base 16) uses the digits 0 to 9 and then A = 10, B = 11, C = 12, D = 13, E = 14, F = 15.

Overflow

Happens when the result needs more bits than there are.

Left shift

Moves every bit left and fills the gap on the right with 0. Each place multiplies the value by 2.

Database

An organised, permanent store of data that can be searched, sorted and updated.

Record

One row

Field

One column: one piece of data stored for every record.

Primary key

A field whose value is different for every record, so it identifies each one.

Foreign key

A field in one table that holds the primary key of another.

Data redundancy

(the same data stored more than once)

SQL

(structured query language) asks questions of a database.

Personal data

Data about an identifiable living person.

Machine code

Binary instructions the CPU carries out directly. Each processor family has its own.

Assembler

Translates assembly language into machine code, one instruction for one instruction.

Network

Two or more devices connected so they can share data and resources.

LAN

(local area network): a small area such as one building; the organisation owns the hardware.

WAN

(wide area network): a large area, linking LANs over lines rented from other companies.

Client-server

A central server stores files, accounts and services; clients request them.

Peer-to-peer

Every computer is both client and server.

Star topology

Every device has its own cable to a central switch.

Mesh topology

Devices are linked to several others, so data can take another route if a link fails.

Internet

A worldwide network of networks.

World Wide Web

The collection of pages reached over it.

The cloud

Remote servers that store data and run services

MAC address

48 bits, six pairs of hex digits such as 3C:22:FB:9A:01:7E, fixed into the NIC when it is made; used on the local network.

Casting

Changes a value's type

Variable

A named place in memory whose value can change.

MOD

Gives the remainder: 17 MOD 5 = 2.

DIV

Gives the whole number part of a division: 17 DIV 5 = 3.

Malware

Software written to cause harm or to steal.

Social engineering

Tricks them into giving away information or access.

Phishing

Fake emails or texts that look genuine and push you to click a link or give details.

Blagging

Inventing a story, often by phone, to get information

Shouldering

Watching someone type a PIN or password.

Brute force attack

Try every possible password, or a list of common ones, until one works.

Denial of service (DoS)

Flood a server with requests so real users cannot get through.

SQL injection

Type SQL into an input box on a site that puts input straight into its database queries, so the extra code runs.