OCR GCSE Computer Science - Paper 1 Key terms

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 performed 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

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 - a clock speed of 3Ghz means that 3 billion FDE cycles run every second

Virtual memory

Virtual memory 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 storage

Data is stored on multiple servers in a remote location
ADV: secure, can be accessed anywhere, no need to buy hardware, backed up by host
DIS: needs internet, download and upload can be affected by internet connection, potential security issues, unclear who owns data in the cloud, could be expensive

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, eg connecting bluetooth headphones to a phone

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)

hardware that allows a device to connect to a network

Switch

connects devices on a LAN - is intelligent and routes data where it needs to go

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

All devices connected to central switch or server controlling the network
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

Devices correctly directly or indirectly to all other devices. No need for central server. Data sent along fastest route.
ADV: faster
DIS: expensive

MAC Address

assigned to all devices, unique and cannot be changed, permanent, identifies the actual device. Used for communication on the same network

IP Address

assigned either manually or automatic, the location of your device on the internet. Static IP addresses are permanent and used to connect printers in a LAN or websites on the Internet. Dynamic addresses are allocated by a server each time the device accesses a network

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. Responsible for splitting data into packets and reassembling them.

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. Allows email to be synchronised across multiple devices.

Simple Mail Transfer Protocol (SMTP)

used to send emails, used to transfer emails between servers

Layer

Group of protocols which ahve similar functions. Self-contained. Each layer serves the layer above.
ADV: breaks network communication into manageable pieces. Self-contained so a layer can be changed without affecting other layers. Forces companies to create compatible hardware/software.

Application Layer

Allows software to communicate with network using protocols, eg browser communicates with WWW using http or https

Transport Layer

controlling data flow - splitting data into packets and checks data sent/delivered correctly, uses TCP

Network (Internet) Layer

Makes connections between networks, adds IP address headers to packets, using IP

Data link Layer

passing data over physical network, eg Ethernet

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

SQL is a programming language used to search and query databases. An injection adds SQL commands for example to a login to access a database

Penetration Testing

organisations employ specialists to simulate potential attacks on their network

Anti-malware Software

designed to find and stop malware from damaging a network

Encryption

data is scrambled so that it is meaningless to anyone who does not have the key to decrypt it

Freedom of Information Act

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

Data Protection Act

Law to protect use of data by organisations. 8 principles. Replaced by GDPR. Data must be held securely, kept up to date and not transferred outside the EEA.

Computer Misuse Act

Law against computer misuse, covers unauthorised access to data, changing/editing data and spreading viruses

Copyright Act

protect intellectual property - anything someone has created

Cache

Very fast memory, close to CPU. Stores regularly used data for quick access. Low capacity and very expensive.

Cores

A multi-core processor will have 2, 4 or 8 processors which can process data independently of the rest. The more cores, the more instructions can be processed, so the faster the data can be processed

Comparing storage

Cost, speed, capacity,
portability, reliability

Fibre optic cable

Data transmitted as light. High speed but expensive. Do not suffer from interference and can transmit data over long distances

Copper wire (coaxial)

Data transmitted over copper wires. Subject to interference. Traditional phone networks use copper.

Wi-fi

Radio waves transmit data. Easy to set up wireless network and generally cheaper. Limited range and subject to interference between channels and blocking by physical objects, eg walls.

Internet

A global network connecting millions of computers, making it possible to exchange information. Biggest WAN.

URL

Uniform Resource Locator - addresses used to access web servers

Ethical

What is considered right and wrong by society

Legal

What is considered right and wrong in the eyes of the law

Cultural

How groups of people with particular beliefs are affected

Environmental

Impact on the natural world

Stakeholder

A person/group of people who are affected by the actions of a company/organisation

Privacy issues

Social media, employee monitoring, cookies, sharing of data

Censorship

Controlling what people can access on the Internet

Surveillance

Monitoring what people do on the Internet