- Created by: Avril w
- Created on: 27-10-18 11:56
The central processing unit
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 and Output Devices
Keyboard - for data entry
mouse - for making desicions
barcode scanner - reads light that is relected back to it
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