Computer input device
Keyboard
mouse
joystick
Light pen
trackball
scanners
graphic tablet
microphone
magnetic ink card reader (MICR )
optical character reader (OCR)
bar code reader(BCR)
optical mark reader (OMR)
Keyboard
It is the most common and very popular input device which helps to input data to the computer.
keyboard are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for windows and internet.
S.No. keys and Description
1. Typing keys
These keys include the letter keys
(A-Z) and digit keys (09) which generally give the same of typewriter.
2. Numeric keypad
It consists of a set of 17 keys .
3. Function keys
The twelve function keys are present on the keyboard which are arranged in row at the top of the keyboard.
4. Control keys
It includes four directional arrow keys Control keys also include home , end , insert, delete, page up , page down etc.
5. Special Purpose keys
Keyboard also contains some special
purpose key such as enter,shift , caps lock,Num Lock, space etc.
Joystick
It is also a pointing device which is used to move the cursor position on a monitor screen it is a stick having a spherical ball at its both lower and upper ends it mainly used in Computer aided designing si a Di and playing computer game
Light pen
Light pen is a pointing device similar to a pain.
Trackball
Trackball is an input device that is mostly used in notebook or laptop computer.
Scanner
Scanner is an input device which work more like a photocopy machine .
Microphone
It is an input device to input sound that is then store in digital form.
Magnetic ink card reader (MICR)
It is generally used in bank as there are large number of cheques to be processed everyday.
Optical character reader ( OCR)
It is an input device used to read a printed text.
Barcode reader
It is a device used for reading barcoded data (data in the form of light and dark lines).
Optical mark reader
It is a special type of optical scanner used to recognise the type of all mark made by pen or pencil.
Computer output
Monitor common called as visual display unit are the main output device of the computer .
There are two kinds of screen used for monitor
Cathode ray tube
Plat pannel display
Cathode ray tubes (CRT )
The CRT display is made of small pixels element called pixels . The smaller the pixels the better image resolution .
Plat pannel display monitor
It refers to a class of video device, that have reduced volume weight . Requirement of composition to the CRT. Current used of FPD include computer, video game, laptop, calculator , monitor and graphic displayed.
printer
printer is an output device which is used to print information on paper.
There are two types of printers:-----
impact printer
non impact printers
impact printer
It print the character by striking them on the ribbon which is them based on the paper.
Non impact printer
It print the characters without using the ribbon. This printer print a complete page at a time.
These printer are of two types :----
lasser printer
Inkjet printer
Lasser printer
these are non impact page printer. They are used lasser light to produce the dot needed on the character to be printed on the page.
Advantages
very high speed
very high quality output
good graphics qualities
Inkjet printer
inkjet printer are non impact printer based on new technology.
Advantages
high quality printing
Computer memory
A memory is just like a human brain. It is used to store data and instruction .
Computer memory is the storage space in the computer.
the memory is divided into large number of small parts for cell.
memory is of three types
cash memory
primary and main memory
secondary memory
cash memory
it is a very high speed semiconductor memory which can speed up the CPU.
It act as a buffer between the CPU and the main memory.
The part of data end program are transferred from the display.
Advantage
It store the data for temporary use.
It is the faster than the main memory.
disadvantage
It has limited capacity
It is very expensive
Primary memory and main memory
It holds only those data and instruction on which the computer is completely working. It is divided into two sub category is RAM and ROM .
Secondary memory
This type of memory is also known as external memory or nonvolatile. It is slower than the main memory . These are used for storing data information permanently, the content of secondary memory are the first transfer to the main memory and then the CPU can access it .
example
CD -ROM ,CD- ROM, DVD
RAM ( random access memory )
RAM is internal memory of the CPU for storing data program and program result. It it is volatile that is data store in it is lost. When we switch off the computer or if their is power failure. RAM is small both in terms of its physical size and in the amount of data it can hold .
RAM is of two type :----
Static RAM(SRAM)
Dynamic RAM (DRAM)
Static RAM
It indicate that the memory is content as long as power is being supplied . Data is lost when the power gets down due to volatile nature .
dynamic RAM
dynamic RAM unlike SRAM must be continued refresh in order to maintain the data . It is used for most system memory as it is cheap and small.
Read only memory (ROM )
This memory from which we can only read but it cannot write on it. This type of memory is non volatile .
This information is store permanently in such memory during manufacture.
Types of ROM
MROM (mask ROM)
PROM (programmable ROM)
EPROM
Advantages of ROM
1. Non- volatile in nature.
2. Cheaper than RAM
3. Easy to test
4. Static and do not require refreshing
5. Content are always known and can be verified.
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