Write a note on input and output devices. Distinguish between human data input devices and source data capture devices.

Ans:

The input device is any machine that feeds data into a computer. The input devices are:

i)- Keyboard:- Keyboard is an input device consisting of a set of typewriter keys that enable us to enter data

into a computer. Computer keyboard are similar to electric typewriter. Keyboard has the following keys.

Alphabetic keys (A to Z, a to z) Alphanumeric keys (0 to 9).

Special keys. Functions keys, control keys, arrow keys caps lock key, and so on.

ii). Mouse:- Mouse is a device that controls the movement of the curser or pointer on a display screen. A mouse is a small object we can roll along a hard flat surface. As we move the mouse the pointer on the display screen moves in the same direction.

iii). Joystick:- A lever that moves in all directions and controls the movement of a pointer or some other display symbols. A joystick is similar to a mouse except that with a mouse the cursor stops moving as soon as we stop moving the mouse. With a joystick the pointer continuous moving in the direction the joystick is pointing. Joysticks are used mostly for computer games but that are also used occasionally for CAD/CAM systems and other applications.

iv). Scanners:- Scanner is an input device that can read text or Picture printed on paper and translates the information into a form that the computer can use. A scanner works by digitizing an image dividing it into a grid of boxes and representing each box with either a zero or a one. We can send the picture or other images

to compute.

v). Digital Camera:- Images can be input into a computer using a digital camera. These images can then be manipulated in many ways using the images tools. The digital camera takes a still photograph, stores it and then sends it as digital input the computer. The images are then stored as digital files.

vi). Bar Code Reader: The bard code identifies the product to the supermarkets, computers, which has a description and the latest price of the product the computer automatically tells the point of sales terminal what the price is.

vii). Light Pen. Light pen is an input device that utilizes a light sensitive detector to select objects on a display screen. A light pen is similar to a mouse except that with a light pen we can move the pointer an  select objects on the display screen by directly pointing to the objects with the pen.

OUTPUT DEVICE:

- An output device is any machine capable of representing information forms a computer. Output devices include display screens, loudspeakers, printers, plotters etc.

i). Monitor: Monitor is displays output. We can see the result by monitor. It is look like a T.V screen. There are many ways to classify monitors. The most basic is in terms of color capacities separates monitors into three classes.

Monochrome: Monochrome monitors actually display two colors, one for the background and one for the foreground. The colors can be black and white, green and black or amber and black.

Color: Color monitors can display anywhere from 16 to over I million different colors it is also called RGB monitors because they accept three separate signals red, green, and blue. An RGB monitor consists of a vacuum tube with three electron guns one each for red, green, and blue at one end and the screen at the other end.

Classification of Monitors.

1). Digital Monitor. 2). Analog Monitor.

1). Digital Monitor: A digital monitor accepts digital signals rather than analog signals all monitors use CRT technology, which is essentially analog. The term digital, therefore, refers only to the type of input received from the video adapter. A digital monitor then translates the digital signals analog that controls the actual display.

2). Analog Monitor: This is the traditional type of color display screen that has been used for years in televisions. All monitors based on CRT technology are analog. Some monitors are called digitals monitors because they accept digital signals from the video adapter.

ii). Printer : Printer is a device that prints text or picture on a paper and in many cases on transparencies and other media. There are many different types of printers.

Daisy wheel printer: There is a type of printer that produces letter quality type. A daisy wheel printer works on the same principle as a ball head typewriter. The daisy wheel is a disk made of plastic or metal on which characters stand out in relief along the outer edge.

b). Dot Matrix Printer: Dot-Matrix printers create characters by striking pins against an ink ribbon. Each pin makes a dot and combinations of dots from characters and pictures. Dot-matrix printers vary in two important characteristics.

Speed: given in characters per second the speed can vary from about 50 to over 500. Print Quality: determined by the number of pins it can vary from 9 to 24. The best dot-matrix printers 24 pins can produce near letter quality type.

c). Ink-Jet Printer: Ink-jet printer work by spraying ionized ink at a sheet of paper. Magnetized plates in the inks path direct the ink onto the paper in the desired shapes. Ink jet printers approaching that produced by laser printers. A typical ink jet printer provides a resolution of 300 dots per inch.

d). Laser Printer: Laser printer utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum.

Disk Drives : Disk drives facilitate to read or write a disk. Floppy disks are transportable form one pc to another. Hard disk is fixed inside the system unit and has much higher storage capacities than floppies. Hard disk: Hard disk is a magnetic disk on which we can store computer data. The term hard is used to distinguish it from a soft or floppy disk, hard disks hold more data and are faster anywhere from 10 MB to several Gigabytes. A hard disk consist of several platters, each platter require two read/write heads. One for each side. All the read/write heads are attached to a single access arm so that they cannot move independently.

Magnetic Tape: Magnetic tape is a magnetically coated strip of plastic on which data can be encoded tape for computer are similar to the tapes used to store music. Some personal computers, in fact, enable us to use normal cassette tapes.

Floppy Disk: Floppy disk is a soft magnetic disk it is also called floppy because it flops if you have wave it. Most hard disk floppy disks are portable, because we can remove them from a disk drive. Floppy disk are slower to access than hard disk and have less storage capacities, but they are less expensive and are portable.

Zip Disk: These are high capacity floppy disk drives developed by the Lomega Corporation. Zip disks are slightly larger than the conventional floppy disks, and are about twice as thick. They can hold 100 MB of data. Because they are relatively inexpensive and durable, they have become large files. 

Optical disk: These are a storage medium from which data is read and to which it is written by lasers. Optical disks can store much more data up to 6 gigabytes. There are three types of optical disk.

1). CD-ROM: CD-ROM stands for Compact Disk Read Only Memory. The data is permanent and can be read any number of times, but CD-ROMs cannot be modified.

2). WORM: WORM stands for write once read many with a worm disk drive we can write data onto a worm disk, but only once. After that the worm disk behaves just like a CD-ROM.

3). CD-RW: CD-RW stands for (Compact Disk Re-writ able). This is a new type of CD disk that enables to write onto it in multiple sessions. One of the problems the CR-R disks is that we can only write to them once. With CD-RW drives and disks we can treat the optical disk just a floppy or hard disk, writing data onto it multiple times. The first CD-RW drives became available in mid-1997. They can read CD-ROMs and can write onto today’s CD-R disks, but they cannot write on CD-ROMs.

Plotter: Plotter is a device that draws pictures on paper based on commands from a computer. Plotters differ from printers in that they draw lines using a pen. Multicolor plotters use different color pens to draw different colors.

Human data input devices

A human interface device or HID is a type of computer device that interacts directly with, and most often takes input from, humans and may deliver output to humans. The term "HID" most commonly refers to the USB-HID specification. The term was coined by Mike Van Flandern of Microsoft when he proposed the USB committee create a Human Input Device class working group. The working group was renamed as the Human Interface Device class at the suggestion of Tom Schmidt of DEC because the proposed standard supported bi-directional communication.

Source data capture devices

Data capture devices provide another level of security to prevent critical human error. CI Solutions offers a complete line of data capture tools and products to help you create and manage your identity verification systems.

As technology advances, it becomes easier and easier for people to forge credentials, but data collection devices help prevent this fraud. If you make or use photo badges or ID cards, magnetic strip readers provide an additional form of authentication that is virtually impossible to forge or tamper with. In order to validate the authenticity of a visitor, staff, or employee badge, the data about that person is encoded onto the ID card using the magnetic strip. When they enter your facility, requiring them to scan their ID card in, a magnetic strip reader will validate that the card is genuine. We offer ID card magnetic strip readers, as well as card writers, which imbed the information on the magnetic strip.

Another secure option is digital signature verification using signature capture pads. Access control is based on the verification of a security badge, along with a matching signature that must match the signature put on file at the time the security badge was created. Other secondary verification measures, such as PIN numbers, can easily be forgotten or compromised. But a signature is unique - it is never lost or stolen and is a socially accepted method of verifying identity.