common CPU components

ALU-Arithmetic and Logical unit- perform logical and arithmetic operations

CU-control unit- co-operates all the processes flowing in and out of the processor

Cache memory- is a very quick, immediate storage that is located very near the CPU

Programme Counter- PC-

Memory Address Register- MAR- holds the address of the next instruction and is to be executed in memory

Memory Data Register- MDR- holds the date fetched or to be written to the main memory.

Accumulator- holds results of calculations that have been done by the ALU

System bus- parrel wires that connect two or more independent components of a computer system in order to pass signals between them

Address Bus:

• carries address from the processor to the main memory or other input/output device.
• the processor generates an address
• all data/instruction return to the data bus
• Uni-directional (one way)

Data Bus: carries instructions from main memory(RAM) or secondary storage(hard disk, DVD…) to the processor(CPU), this is bi-directional (two-way)

Control Bus:

• control signals that have been sent along the control bus
• e.g. memory read +memory write- these are instructions that the control bus carries out.

peripherals- devices not directly connected to the CPU e.g. mouse, keyboard and printers

RAM-Random Access Memory- holds data/instructions that are currently in use by the computer

• located on the motherboard
• directly accessible by the processor
• all data/instructions are lost once power is turned off(volatile)

ROM- read only memory- instructions are permanently etched on a ROM chip

• when power is turned off, instructions still remains in the ROM chip(non-volatile)
• BOOTSTRAP LOADER is held in the ROM

EEPROM-electronically erasable programmable read-only memory-e.g. sim cards/ flash memory- instructions/data can be erased electronically and replaced

Secondary storage used for Long term storage of data and instructions e.g. hard disk drive, DVD-R(read). flash memory