GCSE Computer Science

Algorithm

A sequence of steps to be performed to solve a problem

Computer Program

An implementation of an algorithm

Data Structure

Specialized format for storing and organizing data

Procedure

A names section of code which performs a task and does not return a value

Function

A named section of code which performs a task and returns a value

Parameter

A special type of variable which can be passed through sub-routines

Scope

The reach of a variable/data structure

Computer System

A combination of software and hardware

Character

Single Value "a" or "9"

Integer

Whole Number

Boolean

True or False Value

ASCII

Character Set: Limited to 7 bits, only applicable in Latin based languages

Real

Integer or Decimal Number

Binary

Composed of 1's and 0's

Hexadecimal

Composed of Integers 0-9 and Strings A-F

Denary

Composed of Digits 0-9

Run-Time Error

Error that occurs while the program is running

Unicode

Alternative character set

Iteration

The process of repeating steps

Selection

A question is asked and from the response several paths can be taken

Sequence

The order in which instructions are performed

Logic Error

An error in the logic of the code which causes it to run incorrectly but not crash

Syntax Error

An error in the syntax of the code Will cause the program to crash

Sample Rate

The frequency at which samples are taken

Requirements

When the team decides what the software needs to do, To think about what the user will want the program to do

Design

Working out the smaller details of the program by breaking it down into smaller chunks

Implementation

The program code is written

Testing

Testing the program under various conditions to make sure it is going to work

Evolution

Maintaining and updating the program

Lossy Compression

Removes some of the file's original data to reduce file size

Resolution

How tightly packed the pixels are

Bit Map Image

Images composed of lots of pixels

Vector Image

Image created in graphics packages and consist of shapes called objects

Lossless Compression

Various algorithms are used to find parts in the data that are repeated

Ring Topology

Fast data transfer but if one machine fails the whole network will fail.

Bus Topology

Easy and cheap to install but if the main cable fails the whole network will crash

Star Topology

Reliable and high-performing but expensive to install and if a hub/switch fails the devices will not have network connection

CPU

Brains of the computer. Mainly processes and uses data to perform taks

GPU

A chip/processor designed to boost the performance of games and graphics

RAM

Primary Storage device which allows data to be stored and retrieved on the machine

Volatile Memory

Memory which only maintains it's storage while the machine is active

Non-Volatile Memory

Memory which maintains it storage whether or not the machine is active

Logic Gate

A diagram which represents boolean logic

Virtual Memory

Memory that appears to be main storage although most if it is held in secondary storage

Cache

Memory that is easily accessed by the CPU and is very fast

Secondary Storage

Non-Volatile memory that is not directly accessible by the CPU

Optical

Data is recorded by making marks in a pattern that can be read back with the aid of light.

Magnetic

A mechanical device in which the media is inserted

Solid State

A grid of electrical cells which quickly send and receive data

NOT gate

A logic gate that takes in 1 input & outputs the opposite

AND gate

A logic gate that takes in 2 inputs and only outputs True if both inputs are True

OR gate

A logic gate that takes in 2 inputs and outputs True if either inputs are True

Truth table

A table which holds possible states on inputs and shows the corresponding final output of a logic diagram

Logic Diagram

A diagram combining multiple logic gates to show the inputs and final output of a system

Boolean Logic

Logic which can only produce a True or False outcome

Hardware

The physical elements of a computer system

Sotware

The logical programmed parts of a computer system that tells the hardware how to function

Embedded system

A system developed for a single, or set purpose. E.g. A washing machine, microwave, digital watch

General Purpose System

A computer system that can change its purpose by adding more software

ROM

Non Volatile. Small area of memory which holds the boot up program.

Device Driver

A program stored on the hard drive that tells the computer how to communicate with a hardware device such as a printer, mouse, or keyboard.

Defragger

System software which tidies up the physical locations of where data is saved on a storage device.

Scheduler

System software which establishes the order in which instructions are executed by the processor

GUI

A User Interface which incorporates the four elements of Windows, Icons, Menus, & Pointers

System Software

software responsible for the general operation of a computer system, including the operation of hardware, running application software, and file management

Application Software

computer software created to allow the user to perform a specific job or task. eg. Word, Excel, browsers, games

Autoupdate

A scheduled patch to software (usually system software) to ensure that it is completely up to date with the latest features.

Firewall

A security system consisting of a combination of hardware and software that limits the exposure of a computer or computer network to attack from crackers

Spyware

A computer program which is installed without permission, sometimes through a virus or sometimes as part of the installation of a program. It works by collecting information and sending it back to another source. The information collected could include the websites you have been visiting or what you have been downloading. This can be used for marketing purposes but also for fraud.

Antivirus

System software that is specifically designed to detect viruses and protect a computer and files from harm

Computer Virus

a software program capable of reproducing itself and usually capable of causing great harm to files or other programs on the same computer

Computer Worm

Self-replicating program designed to carry out some unauthorised activity on a victim's computer. This software can spread themselves from one computer to another without any assistance from victims.

Trojan

A piece of software that appears to be a legitimate application, utility, game, or screensaver that performs malicious activities surreptitiously

Phishing

An attack that sends an email or displays a Web announcement that falsely claims to be from a legitimate enterprise in an attempt to trick the user into surrendering private information

Fetch-Decode-Execute Cycle

This is the process that all Stored Program Computers follow in order to run instructions within the machine. Instructions are stored within main memory as a combination of both instruction & data.

Microprocessor

Another name for the central processing unit that is generally made from a single integrated circuit. Multi-core CPUs are made up of more than one microprocessor.

Control Unit

Component of a processor that directs and coordinates most of the operations in the computer.

Arithmetic Logic Unit (ALU)

The circuits that do the math and logic operations inside the processor. The "gateway" all inputs and outputs pass through.

CPU Register

Internal memory in the CPU. These store information that the arithmetic and logic units need to carry out the current instruction.

Program Counter (PC)

A register inside the CPU which holds the address of the next instruction to process.

Current Instruction Register (CIR)

A register inside the CPU which holds the current instruction (not the data)

Memory Address Register (MAR)

A register inside the CPU which holds the address of the current instruction to process. This allows the actual instruction to be loaded.

Memory Data Register (MDR)

A register inside the CPU which holds the data of the current instruction to process.

Accumulator

A register inside the CPU which holds the running total or result of the current instruction.

Address Bus

A physical wire which transmits memory addresses between the CPU and the RAM

Data Bus

A physical wire which transmits data between the CPU and the RAM

Binary Search

Takes the median of a sorted list, and if it is greater than the input, then the top half of the list is removed, and a new list is created until the correct match is found.

Efficiency of algorithms

Speed, Size, Storage

Bubble Sort

Easy to code, however with a longer list can be very inefficient

Name Five Data Types

Integer, Real, Boolean, String, Character

Definite Iteration

Repeating the process until a desired result with a finite number of iterations, that is calculable. Do Until - Loop

Indefinite Iteration

Repeating an iteration that is conditional, and may be repeated infinitely. While-End While

Nested Selection

A selection within a selection

=

Equal to

<>

not equal to

<

less than

greater than

Abstraction

Abstraction is the process of removing all unnecessary information from a set of instructions so that the aim of the instructions is not distracted from and so that the final product is as good as possible. The abstracted data is simpler and more relevant to the operation. Abstraction can speed up the program.

<=

less than or equal to

=

greater than or equal to