Computing - Hardware

GCSE hardware definitions

hardware

The physical components of a computer system

peripheral

Hardware on the periphery of a computer system. The input and output hardware of a computer system

CPU

The main part of the computer

Stored program concept

Processor architecture which stores instructions and data in memory and executes them sequentially using the ALU

Control unit

Part of the CPU that decodes instructions and coordinates the actions of the other parts of the CPU

ALU

Performs calculations e.g. x = 2 + 3 and logical comparisons e.g. IF x > 3 on data in the CPU.

Register

Fast temporary storage within the CPU

Control unit

Decodes instructions. Sends signals to control how data moves around the CPU.

Fetch

Decode

Fetch

Instructions are fetched from memory one at a time into the CPU

Decode

The Control unit decodes the instructions - looks it up in the processor's instruction set to work out what it means.

Execute

The instruction is carried out

buses

Wires that connect the CPU to other components in the computer eg memory. A bus can be uni-directional - information travels in one direction only or bi-directional - information travels to and from components

Address bus

Carries the address of a location in memory. It is uni-directional

Data bus

Carries the data that was stored in the memory location to the CPU or carries the data from the CPU to a location in memory where is to be stored. It is bi-directional.

Control bus

Carries the signals that control the actions of the CPU eg read or write

clock

the electronic unit that synchronises the actions of the CPU. The higher the clock speed

RAM

Storage location for data and instructions that is accessed by the CPU. Main memory is volatile ie data and instructions are lost when the power is turned off

Secondary Storage

Storage location for information. It is not directly accessed by main memory. Information on secondary storage is loaded into main memory. Programs and data are stored on secondary storage when not in use. Secondary storage has a larger capacity than main memory.

Optical Disk

A secondary storage media which stores data as pits and lands on a shiny surface. A pit is 0 and a land is 1. Data is written by being etched by a laser. Data is read using a laser and easring the reflected light. Use: music

Magnetic Disk

A secondary storage media which uses a magnetic material to save the data. Areas are magnetised as north and south. Hard disk drive. Use: systems and applications software. High capacity. Medium data access speed. Low portability (except for portable drives). Reliable but not durable. Medium cost.

SSD

A secondary storage media which stores data by trapping electrons in pools. A pool of trapped electrons is a 0 as it stops the flow of current. Flow of current is a 1. Memory cards & solid state hard drive (SSD). Use: digital cameras and smartphones. Medium capacity. High portability. Reliable and durable. No moving parts. Fast data access speed. High cost.

Capacity

The amount of data a storage device is able to store.

Speed

The read/write access speed of a storage device.

Durable

How resistant to damage and wear a tear a storage device is. Devices with low durability will wear out easily over time.

Price

The relative price of a storage medium

Embedded system

A small computer that is part of a larger device eg a washing machine. The embedded system performs one specific function and is not easily changed. It is programmed for efficiency. It is a microprocessor on which there is the CPU

sensor

A piece of hardware in a device that detects and responds to some type of input from the physical environment – an input device

actuator

A piece of hardware in a device that creates motion – an output device

Real time

A computer system that responds immediately to an external event or request eg systems in cars and planes

Internet of Things

An embedded device that is linked to the internet so it can communicate with other computers