INPUT, OUTPUT AND MEMORY DEVICES

An Input Device is any hardware component used toenter data, programs, commands and user responsesinto a computer.There are a variety of input which are used bycomputers. Some of them are general purpose, thatis, they may be used by any computer.The input devices are as follows:

The KeyboardKeyboard is a typewriter like a device which is used to type in the letters, digits and commands.Working: Each key when pressed send a digital code to the computer that determines when key has been pressed.Advantages: Most common and reliable of inputting data. Available in variety of formats.Disadvantages: Not useful for entering pictures, etc. Very slow for selecting various objects on screen or moving object.

The MouseThe mouse is a pointing device with a roller on the base. Mouse controls movement of a pointer. Working: When a mouse moves on a flat surface, the cursor on the screen also moves in the direct of the mouse movement.Types: Mechanical, Optical and Wireless mouse.Advantages: Ideal for pointing objects on desktop. Most familiar and easy to use pointing device.Disadvantage: Need a flat space close to computer. A mouse cant easily be used by a note book.

Light PenA light pen is used as a pointing device. It consists of a photocell mounted in a pen shaped tube.Working: When a pen is brought in front of a picture elements of the screen, it senses light coming from the limited field of view.Advantages: Easy to use. Can directly draw on screen.Disadvantages: Not very accurate while drawing. Expensive compared to other pointing devices.

Touch screenTouch screen is a type of display that has touch-sensitive transparent panel covering the screen.Working: A grid of light beams criss-cross the compiler screen. When you touch the screen, the rays are blocked and computer senses and identifies the object which u want.Advantages: Easy to use. No training is required.Disadvantages: Not suitable for inputting bulk data. Not very accurate while pointing small areas.

Graphics TabletA Graphic Tablet enables you to enter drawings and sketches into a computer.Working: The tablet contains electronic circuitry that enable it to detect movement of the cursor and translates the movements into digital signals that it sends to the computer.Advantages: Very useful in environment involving move of drawings etc. Disadvantages: Not very useful for pointing and clicking object.

JoystickThe joystick is a device that lets the users move an object on the screen.Working: A joystick is a stick set in two crossed grooves and can be moved left or right, front or back. It is sensed by a potentiometer.Advantages: Useful to play computers on computer. Gives immediate feel of direction.Disadvantage: Involves more arms and wrist movement. Not very useful for clicking objects.

Microphone

Microphone sends sound input to computers through a special input devices. Working: A mic converts the sound received into computers format.Advantages: Useful for inputting audio which cant be input through other devices.Disadvantages: Need specific and additional hardware called Soundcard.

Optical Character Reader

An optical character reader is used to read character of special type font printed on conventional paper with ink.Working: The characters are examined by passing them under a strong light , which differentiates light from inked areas.Advantages: OCR is faster than typing a document which is printed form.Disadvantages: You need to buy scanner and OCR. Its not completely accurate.

Scanner

A scanner is a device similar to a photocopier. A scanner creates a electronic form of image which can be manipulated.Types: Hand-held, Flatbed, Drum Scanners.Advantages: It is accurate and can produce images with higher resolution.Disadvantages: Image can take up a lot of memory space. The output depends on the quality of the document

Optical Mark Reader

Optical Mark Reader transcribes the marks into electrical pulses which are transmitted to the computer.Uses: Objective types answer paper, various type of surveys and order forms.Advantages: A quick and reliable way of inputting large volumes of simple data.Disadvantages: Cant be used for bulk inputs.

Smart Card reader

The Smart Card Reader can read information on smart cards are called smart-card readers. Smart card contains a microprocessor that retains certain security and personal data in its memory at all times

Bar Code Reader

A bar code reader emits a beam of light which reflects off the bar code image.Advantages: Fast and reliable method of inputting data. Can read from curved or upside down surface.Disadvantages: Input is limited to a number code.

Biometric Sensors

Biometric is a technology that verifies a persons identity by measuring a unique-to-the individual biological trait.

Web Camera

A webcam is a loosely used term for any camera that generates images that can be accessed by and displayed on web browsers through servers

The Output Devices produce output of themachine in human readable form. To allow this,the computer must be connected to an outputdevice.The output devices are as follows:

MonitorsMonitor is the most common form of output from a computer. The picture on a monitor is made up of thousands of tiny coloured dots called pixels.They are five types of monitor :~CATHODE RAY TUBE (CRT):The CRT works in the same way as a television – it contains an electron gun at the back of the glass tube. When the electrons strike the phosphor dots they glow to give the colours.~LIQUID CRYSTAL DISPLAY:Liquid Crystal is the material used to create each pixel on the screen. TFT is a variant of LCD technology. LCDs use much less power than a normal monitor.~PLASMA MONITORS:Plasma monitors or PDP (Plasma Display Panels) are flat panel displays. They offer a wide range of contrasts and colours and have a long display life so they can be used for years without going dead.~TOUCHSCREEN MONITORS:Touchscreen monitors are built by combining touch sensitive materials with a durable but sensitive outer material that protects the monitors from fingers but still allows the monitor to detect where a person is placing his fingers.~ORGANIC LIGHT EMITTING DISPLAY (OLED) MONITORS:OLED monitors are created from pushing an electronic current through organic materials, causing these materials to glow. The price of OLED monitors is much more than traditional CRT or LCD monitors .

Cathode Ray Tube (CRT) Liquid Crystal Display (LCD) Plasma Monitor

Touchscreen Monitor Organic Light Emitted Display

PRINTERS

A most convenient and useful method by which the computer can deliver information is by means of printed characters.Printers can be divide into two distinct categories:~Impact Printers~Non-Impact printers

IMPACT PRINTERSIn these printers, there is mechanical contact between the print head and paper. Most common impact printer is Dot Matrix Printer. Dot Matrix Printer(DMP) is the most popular serial printer i.e., it prints one character at a time.

Low operating costs

Can print on continuous stationary.

Using carbonated paper, DMPs can create carbon copies.

ADVANTAGES: DISADVANTAGES:

Non-Impact PrintersIn these printers, there is no mechanical contact between the print head and paper. Advantages of non-impact printer are: high speed, cost effective, better quality.

These printers can primarily be categorised as follows:

Electromagnetic printers: By using magnetic recording techniques, a magnetic image of what is to be printed can be written on drum surface.Thermal printers: An electric pulse can be converted to heat on selected sections of a printing head or on wires or nibs Electrostatic printers: For electrostatic printers the paper is coated with a non conducting dielectric material which holds charges when voltages are applied with writing “nibs”(heads).

Inkjet printers: Some printers direct a high-velocity stream of ink toward the paper

ADVANTAGES: DISADVANTAGES:

Laser Printers: these printers make use of office copier technologies. The toner is then permanently fused on paper with hot or pressure.

ADVANTAGES: DISADVATAGES:

Plotters are the output devices that produce good qualities drawings and graphs. There are two types of plotters : drum plotter and flat bed plotter

PLOTTERS

ADVANTAGES: DISADVANTAGES

SPEAKERS

Speakers have become key sound-output systems. Speakers receive the sound in form of electric current from the sound card and then convert it to sound format. This way pressure vibration are generated that create sounds.

The Main Memory is also know as the ImmediateAccess Store (IAS). IAS holds the data and programsneeded at that instant by CPU. The CPU reads the dataand program kept on secondary storage into the mainmemory, temporary i.e., as long as they are beingprocessed.Units of memory:The computer store and process data in the form ofbinary numbers. A binary number is either 0 or a 1,and is known as bit.

1-Random Access Memory

The Random Access Memory is a form of RAM chips. The data is held in RAM but temporarily the data disappears if the power is switched off. RAM is a volatile memory.

2-Read Only Memory

The ROM is also in the form of chips. The data is not erased when the power is switched off i.e., it is permanent. ROM is a non volatile memory.

Cache Memory

Cache Memory are used in modern, medium and high-speed CPU’s to hold temporarily those positions of the content of main memory which are currently in use. It is a fast and small memory which stores the copy of data which is frequently used from main memory.

Since primary memory has a limited storage capacity and isnot permanent, secondary storage devices are used to storelarge amount of data permanently.There are various types of secondary devices availablethese days. Some most comma storage devices are:~Hard Disk~Floppy disk~CD ROMs~DVDs

Floppy Disks

The floppy disks are one of the oldesttype of portable storage device still inuse.The floppy device enables one totransfer small files betweencomputer and also to store data.A floppy disk is made up of asubstance called Mylar.

Hard DiskThe hard disk memories store information one or more circular platters which are continually spinning.Concentric circle on the magnetized surface of the magnetic disk are known as Tracks. These tracks are divided into invisible segments called sectors.Advantages: Large storage capacity. Permanent storage.Disadvantages: Far slower than RAM/ROM.The disk cannot be transferred to another computer.

Magnetic Tape

Magnetic Tape is a sequential storage medium used for data collection, backup and archiving. It is called a data storage cassette.

Compact Disks (CDs)

1- CD-ROM : This is used to store information and cannot be used to store data.2- CD-R : Data can be recorded on this disk only once.3- CD-RW : CD-RW is a erasable disk you ca write on multiple times.

DVDs1- DVD-ROM : It is a highly capacity optical disk. 2- DVD-R: It is similar to CD-R’s allow users to write on the disc once but read it many times.3- DVD-RW : It is the most writable form DVD. We can erase and read many times from there.

Pen/Thumb- Flash Memories

Flash is a solid state memory i.e., it has no moving parts unlike magnetic storage devices.The data is retained in Flash even when the power is switched of.

Blu-Ray disc

Blu-Ray is a successor to DVD. Blu-Ray’s standard storage capacity is enough to store continues backup copy of mort people’s hard drives on a single disc.

Cloud Storage

Cloud storage is the newest way of storing files and data. The cloud storage s a mechanism not a physical storage device.