GCSE Computer Science (OCR)

Arithmetic Logic Unit (ALU)

Performs operations on data e.g. Addition, subtraction

Control Unit (CU)

Coordinating activities of the CPU

Registers

Quick, small stores of data within the CPU

Memory Address Register (MAR)

Holds memory address for data or a instruction about to be used by the CPU

Memory Data Register (MDR)

Holds actual data or instruction

Accumulator

Stores results of calculations in the ALU

Program Counter (PC)

Holds memory address of the instruction for each cycle

Fetch

The next instruction is retrieved by CPU from main memory

Decode

The instruction is broken down and decided so computer can understand

Execute

The CPU performs what the instructions told

Embedded System

A computer system built within a large device e.g. Camera, washer, car

Volatile

Memory loses its data when power of

Non-volatile

Memory retains its data when power is lost

Random Access Memory (RAM)

Read/write - function is to load open programs and operating system data currently in use - volatile

Read Only Memory (ROM)

Can only be read, can't be changed, stores essential programs to be run in order to boot the computer - non-volatile

Cache

A type memory that stores copies of frequently used data, much faster than RAM, lower capacity - closer to CPU

Buses

Collection of wires that carry signals between various components of the computer system

Central Processing Unit (CPU)

Processes all of the data and instructions that make the system work - can be effected by clock speed, number of cores, cache size

Clock speed

How fast the computer does the FDE cycle

virtual memory

A memory management procedure needed when the RAM is full so a temporary section is made which acts like a part of RAM

Flash memory

Solid state storage, non-volatile, more reliable/durable but can only be overwritten a limited number of times

Graphics Processing Unit (GPU)

Handles graphics and image processing

Optical storage

CD, DVD, Blue-ray

ADV: cheap,easy to transport

DIS: slow, less storage than hard drives, stored data degrades over time, cannot be written over

Magnetic storage

Hard drives

ADV: fast access, stores large amounts of data, low cost

DIS: not very portable, easily be broken

Solid State storage

USB, flash memory, SD

ADV: fast, small, light, easily potable, quiet

DIS: more expensive, storage capacity less, limited number erase/write cycles

Cloud stotage

Data is stored on multiple servers in a remote location

ADV: secure, can be accessed anywhere, no need to buy

DIS: needs internet, download and upload can be effected by internet connection, less control if data is held

Operating System

essential software that links the hardware and other software together and generally manages the computer system

Command-line Interface

Text commands where user has to type in command

Graphical User Interface (GUI)

uses icons and other visual indicators to navigate and issue commands

Utility Software

maintains a computer

Defragmentation Software

reorganises data on the hard drive to put fragmented files back together and moves files to collect all the free space

Backup Software

Full Backup - a copy is taken from from every file on the system

Incremental Backup - only files created or edited since last backup are copied

Compression Software

reduces file size so they take up less space on hard disk

Encryption Software

scrambles data to stop others from accessing it

Open Source Software

source code is made freely available and users can modify it

ADV: free, ,made for greater good, can be adapted

DIS: small, buggy, security holes, no warranties, no customer support

Proprietary Software

only the compiled code is released and the source code is kept a secret

ADV: warranties, well-tested, reliable, cheaper

DIS: expensive, software may not fit user needs

Personal Area Network (PAN)

within the range of an individual person

Local Area Network (LAN)

a network that connects devices close to each other e.g. school, house

Wide Area Network (WAN)

a network within a large geographical area e.g. internet

Bandwidth

amount of data that can be transferred in a given time

Network Interface Card (NIC)

allow a device to connect to a network

Switch

connect devices on a LAN

Router

responsible for transmitting data between networks

Ethernet

a set of standards for connecting computers

Client-server Network

client has connection to server, servers can backup and store centrally but can be expensive and difficult to maintain

Peer-to-peer Network

no central server, each computer equal in responsibility, have to work as both server and a client.

Star Topology

ADV: better performance, rest of network not affected in one fails, simple to add more devices

DIS: wire needed for all devices, expensive

Mesh Topology

ADV: faster

DIS: expensive

MAC Address

assigned to all devices, unique to all devises and cannot be changed, permanent, identifies the actual device.

IP Adress

assigned either manually or automatic, the location of your device on the internet

Packet Switching

split data into packets to be sent across the network, each packet given a number order of data, each router reads packet header and decides which way to send it according to IP rules, packets then arrive and reassemble them in the right order.

TCP/IP

sets of rules for how devices connect on the network.

Hyper Text Transfer Protocol (HTTP)

used to access websites and communicate with web servers

HTTPS

more secure - encryption

File Transfer Protocol (FTP)

used to access, edit and move files between devices

Post Office Protocol (POP3)

used to retrieve emails from a server, holds until download - then deletes from server

Internet Message Access (IMAP)

used to retrieve emails, server holds until you actually delete it- only download a copy

Simple Mail Transfer Protocol (SMTP)

used to send emails, used to transfer emails between servers

Layer

ADV: manageable pieces, self-contained can change without effecting others

Application Layer

turning data into websites

Transport Layer

controlling data flow - splitting data into packets

Network Layer

making connections between networks

Data link Layer

passing data over physical network-

Domain Name Server (DNS)

translates websites' domain name into its IP address

Virtual Network

network that is entirely software based, created by partitioning of some physical network

Blagging

invented scenario to engage a targeted victim in a manner that increases the chance the victim will divulge information

Phishing

used to gain personal information for purposes of identity theft, using fraudulent e-mail messages that appear to come from legitimate businesses.

Shouldering

used to obtain information such as personal identification numbers (PINs), passwords and other confidential data by looking over the victim's shoulder.

Malware

malicious software - computer programs designed to infiltrate and damage computers without the users consent.

Virus

program loaded onto a user's computer without the user's knowledge and performs malicious actions. It can self-replicate, inserting itself onto other programs or files, infecting them in the process.

Worm

program that replicates itself in order to spread to other computers. Often, it uses a computer network to spread itself, relying on security failures on the target computer to access it.

Trojan Horse

program which misleads users of its true intent.

Spyware

aims to gather information about a person or organization without their knowledge

Adware

unwanted advertisements to the user of a computer

Brute Force Attack

trail and error to gain information

Denial of Service Attack (DOS)

hacker stop users from accessing a part of a network, flooding network with useless traffic making computer very slow

Data Interception And Theft

The unauthorized taking or interception of computer-based information. Data theft is the act of stealing computer-based information from an unknowing victim with the intent of compromising privacy or obtaining confidential information.

SQL Injection

programming language used to search and query databases.

Zero-day Attack

before software is released it is tested as much as possible

Penetration Testing

organisations employ specialists to stimulate potential attacks on their network

Anti-malware Software

designed to find and stop malware from damaging a network

Encryption

data is translated into code which only someone with the correct key can access

Data Protection Act

your data should be protected and kept safe from hackers

Freedom of Information Act

allows members of the public to access information held by a public organisation

Computer Misuse Act

stop hacking and cyber crime - stop unauthorized access to private network

Copyright Act

protect intellectual property - anything someone has created

alphanumeric

collective name for letters, digits, symbols

analogue signal

a continuous signal which can't be processed by a computer

argument

a value that a parameter of a subprogram actually takes

ALU

part of CPU that carries out arithmetic and Boolean operations

array

data structure where all data is stored and defined under one variable name

ASCII

A 7-bit character set consisting of 128 characters

assembler

a program that turns assembly language into machine code

assembly language

low-level langauge

authentication

a process for checking user identity

binary

a counting system using base-2 consisting of 0s and 1s

binary shift

moving the bits in a binary number left or right and filling gaps with 0s

BIOS

Basic Input Output System

bitmap image

a graphic made up of pixels

bit

a binary digit either 0 or 1