OCR GCSE Computing

Cache

Cache

Stores frequently used instructions.

Control Unit

Decodes instructions and sends signals to the other components on how to respond to this instruction.

Arithmetic Logic Unit

Responsible for performing arithmetic calculations and logical decisions.

Von Neumann Architecture

Consists of the CPU and Memory which are interconnected and can both store instructions and data.

Registers

A location within the CPU that stores addresses and data which can be accessed quickly.

Program Counter

Stores the next instruction ready to be used.

Accumulator

Stores the results of the arithmetic calculations.

Clock Speed

Controls how many cycles can be processed per second. The higher the clock speed, the more instructions executed per second.

Cores

act as the brain of the CPU → more allow instructions to be split up between the processors.

Embedded System

A computer system that is typically found within another device and is designed to perform a set of dedicated/specific functions.

Real-Time System

A well-defined system with fixed time constraints meaning it will provide an immediate response to an input.

Primary Storage

A medium that holds memory for short periods of time while a computer is running.

Virtual Memory

When the RAM becomes full, the overflow of data normally stored in the RAM will be stored in Virtual Memory which is located on the hard drive.

Volatile Memory

Means when the computer is switched off, data is lost.

Non-Volatile Memory

Has the ability to retain data even when the computer is switched off.

BIOS

Stores instructions required to boot up the computer and is designed to boot up the computer using a POST (Power on self-test).

Secondary Storage

Has the ability to store files even when the computer is switched off, therefore it's a non-volatile form of storage.

Magnetic Storage

Eg. Hard Drive,

which contains a spinning platter with a thin magnetic coating, head moves writing 1’s and 0’s

Solid-State Storage

Eg. USB and SD card

Uses integrated circuits to store data persistently, typically using flash memory.

Cost

How much the device costs per MB.

Capacity

How much space is available on the storage device.

Reliability

how well it can maintain the same level of performance over time.

Durability

How resistant it is to external factors such as being dropped, scratched and how it responds to being in extreme conditions.

Portability

How easy it is to transport from one place to another.

Speed

How quickly the data can be read and transferred from the storage device.

Optical Storage

Eg. CD, DVD, Blu-ray

Any storage type in which data is written and read with a laser.

Sound file size

Calculated using the formula: sound file size = sample rate x duration (s) x bit depth.

Image file size

Calculated using the formula: image file size = colour depth x image height (px) x image width (px).

Text file size

Calculated using the formula: text file size = bits per character x number of characters.

Bit

The smallest unit of data, representing a binary state of 0 or 1.

Nibble

A group of 4 bits.

Byte

A group of 8 bits.

KB

1,000 Bytes.

MB

1,000 KB.

GB

1,000 MB.

TB

1,000 GB.

PB

1,000 TB.

Binary

The language of the computer, consisting of two digits: 1 and 0.

Binary overflow

Occurs when there is not enough space to store a piece of data.

ASCII

consists of up to 256 characters.

Unicode

A universal encoded character set that supports storage of information from most languages.

Colour Depth

Refers to how many possible colours can be represented in each pixel (bits per pixel).

Resolution

Typically described in PPI, which refers to how many pixels are displayed per inch of an image.

Metadata

Data about data; includes information such as dimensions, file type, file size, and resolution.

Sampling

The process of taking samples at regular intervals when recording sound.

Sample Rate

Frequency of samples taken per second, measured in Hz.

Bit Depth

Number of bits per sample affecting sound quality.

Compression

Algorithm to reduce file size for storage efficiency.

Lossy Compression

• data is permanently lost

• impacts the quality

• significantly reduces file size

• eg. JPG

Lossless Compression

• doesn’t remove data

• reversible

• overall quality is retained

• large file size

• Eg. PNG

LAN

Local Area Network covering a small geographical area.

WAN

Wide Area Network covering a large geographical area.

Client-Server Network

This allows files to be stored centrally so workers can access files from any computer and all computers can update the central database. Backups can be implemented

Peer-to-Peer Network

Decentralized network where devices share resources equally. Each would have to perform backup and software updates

Network Interface Controller (NIC)

Hardware to connect a computer to a network.

Switch

Device that directs data to specific network addresses.

Router

Connects different networks and forwards data accordingly.

Wireless Access Point

Converts wired data into wireless signals for devices.

Hub

Connects multiple devices; sends data to all devices.

Domain Name System (DNS)

Translates domain names into IP addresses for access.

Cloud Computing

Delivery of computing services over the Internet.

Web Hosting

Service that stores and serves websites on the Internet.

Network Topology

Structure and layout of a computer network.

Star Network

Each device connects to a central hub or switch.

Mesh Network

Nodes interconnected, allowing multiple data paths.

Partial Mesh

Not all nodes are directly connected in the network.

Packet Switching

Data is broken into packets for efficient transmission.

Bandwidth

Maximum data transfer rate of a network connection.

Network Hardware

Devices required for communication over a network.

Protocols

Rules governing data transmission over networks.

Application Layer

Layer handling data between browser and server.

HTTP

Protocol for transferring hypertext over the web.

HTTPS

Secure version of HTTP using encryption.

FTP

Protocol for transferring files between computers.

SMTP

Protocol for sending emails.

POP

Protocol for retrieving emails from a server.

IMAP

Protocol for managing emails on a server.

TCP/IP

Fundamental protocols for internet communication.

Ethernet

Common wired networking technology.

Wi-Fi

Wireless technology for high-speed internet access.

Bluetooth

Wireless technology for short-range data sharing.

MAC Address

Unique identifier for network interface controllers.

IP Address

Numerical label for identifying devices on a network.

Encryption

Algorithm to secure data by scrambling it.

SQL Injection

used to interfere with queries that an application makes to its database in order to gain unauthorised access to users data

Packet Sniffers

used to intercept data packets on a network which are then analysed

Brute Force Attack

uses automated software to try millions of different password combinations

DDoS Attack

overloads the network by using bots to send useless requests to servers to a point in which is becomes flooded and unresponsive

Malware

Software designed to disrupt or damage systems.

Virus

Self-replicating malware that attaches to files.

Trojan

disguised as a normal file but once downloaded it performs malicious tasks

Worm

Malware that spreads across networks with the user’s action.

Ransomware

Malware that demands payment to decrypt personal data.

Spyware

used to track a user’s activity without their knowledge

Rootkit

Malware that provides unauthorized remote access.

Strong Passwords

Passwords with upper/lowercase, numbers, symbols.

Physical Security

Measures to protect physical access to networks like alarms

Network Forensics

Analysis of network traffic for security breaches.

Anti-malware Software

Programs designed to detect and remove malware.

Penetration Testing

Simulated cyber attack to identify vulnerabilities.