GCSE Computer Science: Internal & External Hardware

Accumulator (registers)

A register which intermediate arithmetic and logic results are stored

Actuator

A mechanical device for moving or controlling a mechanism or system and controlled by a computer system

ALU

Performs arithmetic calculations. All inputs & outputs must pass through here. Acts as a gateway to the CPU.

Back Up

A copy of files to prevent loss of data.

Base

The number of digits used within a number system

Binary

Base 2 number system which can be read by computers

BIOS

Basic Input Output System

CIR (registers)

The instruction in the MDR is now copied to the CIR, and then held whilst being read and executed.

Control Unit

The CU manages the execution of instructions in a processor.

CPU

The processor unit which carries out the fetch,decode, execute cycle using registers and busses

Data Bus

Carries the data from one register to another.

Hard Wired

Devices that are connected to a computer with cables.

Hardware

The physical components that make up the computer i.e. mouse or printer etc.

Immediate Access Store

AKA Memory Unit. Refers to the collective term of RAM and ROM

Internal Memory

AKA Memory Unit. Refers to the collective term of RAM and ROM

MAR (registers)

Memory Address Register. Holds the address that was read from the PC.

MDR (registers)

Memory Data Register. The contents of the address in the MAR is then stored in the MDR.

Memory Unit

Also known as memory or Immediate Access store (IAS) refers to the collective term of RAM and ROM

Primary Memory

Often referred to simply as memory, is the only one directly accessible to the CPU. Primary Memory is often volatile.

RAM

Random Access Memory. The data disappears if the power is switched off, RAM is volatile

Secondary Storage

A device that stores data for a long period of time i.e. hard drive

NOT Gate

A logic gate used to identify a true value when a condition is not met.

AND Gate

A logic gate used to identify a true value when two or more conditions are met.

OR Gate

A logic gate used to identify a true value when one or more conditions are met

GPU

CPU for the Graphics Card which is optimised to produce high quality 3D graphics. This takes the strain away from the main CPU. It is known as a co-processor.

CPU Core

One of a number of processing units inside the CPU. Common to go up in powers of 2

Clock Speed

Indicates how fast the processor is running. Measured in megahertz or gigahertz.

2 Billion Cycles per Second

This is how many processes a 2GHz processor can complete. A process is a full cycle of the Fetch Decode Execute Cycle

Fetch Decode Execute

The cycle which refers to how a Von Neumann Architecture processor receives instructions & data, then processes the instruction.

Cache

A very small, but very fast piece of memory which is part of the CPU. It temporarily holds instructions and data that are ready to be processed.

CISC

This is a processor which holds a complex instruction set which is generally larger & run at a higher clock speed. They are better at processing graphic intensive tasks.

RISC

This is a processor which holds fewer instructions and is more energy efficient. However, they run at a lower clock speed and can be smaller which allows them to be used in smartphones & tablets.

Motherboard

A circuit board which allows the CPU to physically connect to all other hardware in the computer system.

Buses

Circuits within the motherboard that facilitate the transfer of data.

Address Bus

Ciruits which send information about where data needs to go. Is sent from the CPU to the RAM

Bridge

Direct connections between pieces of hardware on the motherboard. Divided into North & South.

Volatile Memory

Memory which only retains data whilst the power is switched on.

Non-Volatile Memory

Memory which retains data even when the power is switched off.

Virtual Memory

When a section of the hard drive is partitioned and used as if it were RAM.

Latency

The time it takes for components / a server to respond to a request. There will always be a short delay to allow for the FDE cycle

Lag

An unacceptable latency time which allows the user to be made aware of the delay in a request response.