INPUT DEVICE

INPUT DEVICE

1)      KEYBOARD: The keyboard is a standard input device. It is a data entry platform of computer system. The layout of keyboard is similar to type write machines. It has large numbers of keys for processing mathematical, logical and string operation. When key is pressed electrical signal is generate which determine which key was pressed. This process is known as encoding.

The computer keyboard uses the same key arrangement as the mechanical and electronic typewriter keyboards that preceded the computer. The standard arrangement of alphabetic keys is known as the Qwerty (pronounced KWEHR-tee) keyboard, its name deriving from the arrangement of the five keys at the upper left of the three rows of alphabetic keys. This arrangement, invented for one of the earliest mechanical typewriters, dates back to the 1870s. Another well-known key arrangement is the Dvorak (pronounced duh-VOR-ak, not like the Czech composer) system, which was designed to be easier to learn and use. The Dvorak keyboard was designed with the most common consonants on one side of the middle or home row and the vowels on the other side so that typing tends to alternate key strokes back and forth between hands. Although the Dvorak keyboard has never been widely used, it has adherents.

2)      MOUSE: Mouse is also important input device used to clicking data purpose. It is a hand held small device used to move the cursor on the screen. 

 

Mouse may be of two types.

i)                    Mechanical mouse

ii)                  Optical mouse

Mechanical mouse: it consists of a rubber ball on the bats when the rubber ball is moved than LED and a photo Decatur interrupt. The light path a number Interrupt so generated is used to report the mouse movement to the computer.

Optical Mouse: Optical mouse using light ray. It uses a special pad. Having a grid of alternative light and dark lines a Led ON THE Bottom of the mouse directs a beam of lights down on to pad, from which it is reflected and sensed by the direction of the bottom of the mouse. As the mouse is move the reflected being is broken is time. A dark line is crossed. The number of pulse as are generated which equals to the number of lines, crossed are sue to report mouse movement to the computer. 

What is ALU

·         What is ALU? Write the function of ALU and control unit.

Ø  ALU stands for Arithmetic logic Unit. It is the main component of CPU. ALU performs all type of mathematical and logical operation such as:

Ø  Arithmetic Operation – Addition, subtraction, multiplication, division, increment, decrement

Ø  Logical Operation – Logical OR, Logical AND, Logical NOT etc.

Ø  Others – Left shift, R6ktr`ight shift, clear.

·         Function of ALU

1)      It accepts operands from registers.

2)      It performs arithmetic and logical operation.

3)      It returns result to memory.

4)      It reads states of and ALU.

·         Function of control Unit.

1)      It generate control signal and sends all the parts of computer.

2)      It controls all types of primary and secondary memory.

3)      It controls the entire peripheral device such as input device, output device and many more.

difference between RAM and ROM.?

·         What is the difference between RAM and ROM.?

RAM	ROM
1)      It stands for Random access memory.	It stands for read only memory.
2)      RAM is temporary type o memory.	ROM is a permanent memory.
3)      It can do both read and write operation.	It can do only Read operation.
4)      RAM lost it's contain, if its power is off.	RAM does not lose its contents if power is off.
5)      It is called volatile memory.	It is called non-volatile memory.
6)      It is expensive.	It is cheaper.
7)      It is of two types. a)      SRAM b)      DRAM	It is of three types. a)      PROM b)      EPROM c)       EEPROM

Difference between primary and secondary memory.

v What is the difference between primary and secondary memory.

PRIMARY MEMORY	SECONDARY MEMORY
1)      It is semiconductor memory.	It is magnetic and optical memory.
2)      It is faster and expensive than secondary memory.	It is slower and cheaper than primary memory.
3)      Primary memories are smaller in size.	Auxiliary memory is larger than primary memory.
4)      Its storing capacity is small.	Secondary memory is permanent.
5)      Processor directly access main memory.	Processor does not access directly secondary memory.
6)      Example: RAM, ROM.	Example: CD, DVD, CD-R, CD-RW etc.