Computer Hardware

Hardware is the physical components of a computer system, they include INPUT, OUTPUT, STORAGE and PROCESSING.

The CPU or the central processing unit carries out all the processes in a computer.

It runs on the FETCH - DECODE - EXECUTE cycle.

The cpu has 3 things that vary its speed:

     - Clock speed (number of cycles per second)

     - Cache memory (temporary, fast access memory)

     - Core processors (more processors can run at the same time)

RAM (random access memory)                                                                    ROM (read-only memory)

Volatile - data lost when power is cut                                                                    Non-volatile

Can be accessed and changed                                                                             Written during manufacture can’t be                                                                                                                                                           changed

Stores programs and data used by computer                                                       Stores instructions for start up

Contains the operating system                                                                               Contains the boot program

Large (4GB or more)                                                                                                 Small (1 or 2 MB)

Virtual memory is a space within the hard drive that is used as RAM when actual ram is full, Virtual memory is slower to access and therefore if MORE RAM is added a computer will run faster.

Flash memory is like ROM because it is non-volatile, but it can be rewritten. It is a portable medium used for saving and transferring data.

Input

Keyboard - for data entry

mouse - for making desicions 

barcode scanner - reads light that is relected back to it

Output

monitor - displays text and images

printer - produces hard coopy on paper

speakers - prodcue sound output

Secondary storage is needed to store data and programs when the computer is switched off.

considerations when selecting it

Capacity, speed, portability, durability, reliability

Magnetic Hard disk                       Optical disk (cd/DVD)                          Flash memory

Reliable                                                    Good capacity                                     Okay capacity

High capacity                                             Low cost                                                   Portable

Low cost                                            Lightweight & portable                            More expensive

magnetic hard disk - Stores operating systems, installed programs

optical disk - Good for transferring files and distributing software

flash memory - Consumes very little power