Computer Science Keyword Lent 2023

CPU

Central Processing Unit - loads and executed a program, coordinates and manages the hardware resources

ALU

Arithmetic Logic Unit - where the actual arithmetic operation are done

CU

Control Unit - coordinates and controls all of the activities taking place within the CPU, receives control signals from the system clock

System Clock

Used to synchronise the operations of the processor components

Clock Cycle / Clock Period

Time taken between two sequential rising edges, 1 clock cycle per second = 1 Hz

Cache memory

When RAM can’t keep up with the speed of processor, cache is used to store data and instructions frequently used

PC

Program Counter - holds location of the NEXT instruction/data address in main memory

MAR

Memory Address Register - the contents of PC copied to here, holds the address of current instruction, then the data it uses, so that it can fetched from memory

MDR

Memory Data Register - holds the actual instruction, and the data that has been fetched from memory

ACC

Accumulator - holds the result of an instruction before it is transferred to memory

CIR

Current Instruction Register - holds the current instruction that the processor is executing

Buses

Set of parallel wires connecting two or more components of the computer

Address Bus

Unidirectional bus carrying the address of data between processor and memory

Data Bus

Bidirectional bus carrying data between the processor, the memory unit and the input/output devices

Control Bus

Carries control signals/commands from CPU in order to control and coordinate all the activities within the computer

Fetch

Causes the next instruction and any data involved to be fetched from main memory

Decode

Decodes the instruction

Execute

The instruction is executed

Embedded System

A system that is made up of both software and hardware and all components are on a single printed circuit board and only carries out specific tasks

ROM

Read Only Memory - stores initial program that runs when computer is turned on (bootstrap), and tells computer where to find the operating system on hard drive, not volatile

BIOS

Basic Input/Output System - can run without a hard drive or other secondary storage, controls basic technical configuration of the computer (e.g. processor speed and system time), stored in the ROM

DNS

Domain Name Service

1. URL received by a DNS resolver server

2. Server queries a DNS root name server

3. Root server responds with the address of the top-level domain server for .com

4. Resolver then makes request to the .com TLD server

5. TLD server then responds with the IP address of the domain’s name server, google.com

6. The recursive resolver sends a query to the domain’s name server

7. IP address for google.com is then returned to the resolver from the name server

8. DNS resolver responds to the web browser with the IP address of google.com

IP

Internet Protocol - Routes packets between router on a WAN

MAC

Media Access Control - Found on the device’s network interface card (NIC), and routes frames between NICs on a LAN

The ‘Cloud”

Term used to refer to services that are delivered over the internet

Advantages of the ‘cloud’

1. Data access from anywhere

2. No longer crucial to back up data

3. Everything is stored and run on a remote computer

Disadvantages for the ‘cloud’

1. Personal data will be stored on another company’s server

2. Requires internet connection

3. Slow internet connection = poor quality of service

IPv4 address

Four 8 bit IP addresses separated by a dot

IPv6 address

128 bit number address represented in hex

Penetration testing

Deliberately trying to find holes in your own system

Anti-malware software

Software that detects bugs and remove malware such as viruses, worms, trojans, and spyware, however some viruses can morph to avoid detection

Firewall

A packet filtering firewall is a network security feature that controls the flow of incoming and outgoing network data

User Access Levels

Users on a network are arranged in groups and each group has different access rights to software, downloads and files that they can use

Password Policy

Passwords are often checked as they are created to make sure that they conform to the parameters given in a required policy

Encryption

A way of securing data so that it cannot be read without the encryption key

Physical Security

CCTV cameras, locks on door or cabinets or security guards

Types of User Interfaces

1. GUI (Graphical User Interface)

2. Menu-driven Interface

3. CLI (Command Line Interface)

4. Voice activated

5. Real - time

Multi-tasking

When an operating system manages many tasks happening at the same time

Memory management

Data used by program is copied to main memory, OS keeps a record of where each program and its data are located, the OS will make sure not to overwrite existing programs and data

Interrupt

A signal emitted by a device attached to a computer or from a program within the computer

Peripheral management

Peripheral hardware is any hardware device that is not inside the computer main body and OS must manage getting inputs from and sending outputs to peripheral devices

File Management

Carried out by the OS and following features are available:

1. Naming files

2. Allocating files to folders

3. Moving files

4. Saving files

5. Copying files

6. Deleting files

User Management

The OS is responsible for user logins and passwords