Arithmetic and Logical Unit

This unit is responsible for performing various Arithmetic operation of addition, subtraction, multiplication, division and relational operations such as equal to, greater than , less than, greater than or not equal to and logical operation etc.

Primary Memory Unit

The main or primary memory stores information (instruction and data) The memory unit is divided into

v Random Access Memory (RAM)

v Read Only Memory(ROM)

RAM

Random Access Memory is used for primary storage in computers to hold active information of data and instructions.

Figure 2.6 RAM (Random Access Mamory)

ROM (Read Only Memory) is used to store the instructions provided by the manufacturer, which holds the instructions to check basic hardware interconnector and to load operating system from appropriate storage device.

Figure 2.7 ROM (Read Only Mamory)

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Units of Memory

The elementary unit of memory is a bit. A group of 4 bits is called a nibble and a group of 8 bits is called a byte. One byte is the minimum space required to store one character.

Other units of memory are:

1 KB(Kilo Byte) = 210 bytes = 1024 bytes

1 MB(Mega Byte) = 210 KB = 1024 KB

1 GB(Giga Byte) = 210 MB = 1024 MB

1 TB(Tera Byte) = 210 GB = 1024 GB

1 PB(Peta Byte) = 210 TB = 1024 TB

Output Devices

These are used to display results on video display or are used to print the result. These

can also be used to store the result for further use.

	Monitor or VDU It is the most common output device. It looks like a TV. Its display may be CRT, LCD, Plasma or touch sensitive.
	Speakers These are used to listen to the audio output of computer.
Printers These are used to produce hard copy of output as text or graphics.
	Dot Matrix Printer This printer prints characters by striking an ink soaked ribbon against the paper. These can be used to generate carbon copies also.
	Inkjet/Deskjet/Bubblejet printersThese all are low cost printers which use a controlled stream of ink for printing.
	Laser PrintersThese printers use laser technology to produce printed documents. These are very fast printers and are used for high quality prints.
	PlottersThese are used to print graphics. It is mainly used in computer-aided designing.

Figure 2.8 Other Output Devices

Communication Bus

In computer architecture, a bus is a system that transfers data between computer

components or between computers.

Address Bus

This is a system of bus, which is used to specify the address of a memory location. The

width of a bus determines the number of memory locations that can be addressed. For

example a system with 64-bit address bus can address 264 memory locations.

Data Bus

This system of bus is a medium, which transfer the data from one place to another in a

computer system.

Control Bus

This system of bus carries the signals that give the report about the status of a device. For

ex one wire of bus indicates whether the CPU is currently reading or writing from the

main memory.

Date: 2015-12-17; view: 923