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#deck:Brainlag::GCSE Computer Science key terms
#tags:brainlag gcse-cs
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.