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                                   : NIRUBINY A/P KARUNAKARAN

INPUT

•  Input is any data and instructions entered into the memory of a computer   

KEYBOARD

Why is the keyboard an input device?

A computer keyboard is considered an input device because it only sends data to a computer and does not receive any information back.

A computer keyboard is one of the primary input devices used with a computer that looks similar to those found on electric typewriters, but with some additional keys. Keyboards allow you to input letters, numbers and other symbols into a computer that can serve as commands or be used to type text.



The following image shows a 104-key Saitek keyboard with indicators pointing to each of the major key sections of a keyboard including the control keys, function keys, LES indicators, wrist pad, arrow keys and keypad.  

 

Keyboard overview

Above is a closer up image of a QWERTY computer keyboard with each of the keys selectable. Hover over any of the keys below to see a description of the key and click any of the keys to open a new page with full details about the key.

Keyboard interfaces

Today, most desktop computer keyboards connect to the computer using either USB or Bluetooth for wireless communication.

Types of keyboards

Today, most keyboards are similar to each other, but may be missing one or more of the sections mentioned earlier (e.g. the keypad). Where keyboards begin to differ the most is with the keyboard layout. While most keyboards use the QWERTY layout, there are still people who use the DVORAK layout.

Laptop keyboards

A laptop keyboard is different from a desktop keyboard to help reduce the size and the overall weight of the laptop. Most laptop keyboards are made smaller by placing the keys closer to each other and not always including control keys or a keypad. For a laptop to have all the same functions of a desktop keyboard, laptop keyboards use aFn key that is used in conjunction with other keys to perform special functions. For example, pressing the Fn key and the up or down arrow on the keyboard shown below, increases and decreases the brightness of the screen.

 

Another difference with a laptop keyboard is the type of switch beneath each key or how the keys feel when pressed down. Some users may even experience more typing errors when typing on a laptop because of how easy it can be to press another key next to the key you intended to press.

Smartphone and tablet keyboards

Today'ssmartphonesandtablets do not come with a physical keyboard, although it may be purchased as an optional peripheral add-on. These devices utilize a thumb keyboard or on-screen keyboard to type messages and enter text into various fields. The image to the right shows an example of the Apple iPhone on-screen keyboard, used on all of apples touch-based devise.

 

  

SCANNER

A scanner may refer to any of the following:

When referring to hardware, a scanner or optical scanner is a hardware input devise  that optically "reads" and image and converts it into a digital signal. For example, a scanner may be used to convert a printed picture, drawing, or document into a digital file which can be edited on a computer. The picture shows an example of a flatbed photo scanner, the Epson V300.

How is a scanner connected?

A scanner can be connected to a computer using many different interfaces although today is most commonly connected to a computer using a USB cable.

• FIREWIRE
• PARALLEL
• SCSI
• USB

Firewire

Alternatively referred to as IEEE-1394, FireWire is a digital bus with a bandwidth of 400-800 Mbps. It can handle up to 63 units on the same bus, and is hot swappable . It was first developed by Apple . Users more familiar with USB can consider FireWire similar to USB, as they has many similarities. Like USB, FireWire has dozens of different devices such as removable drives and cameras.

Parallel

Less commonly referred to as the Centronics interface or Centronics connector after the company that originally designed it, the port was later developed by Epson. The parallel port is found on the back of IBM compatible computers and is a 25-pin (type DB-25) computer interface commonly used to connect printers to the computer. Below is an example of the DB25 interface found on the back of the computer.

SCSI

Short for Small Computer System Interface, SCSI is pronounced as "Scuzzy" and is one of the most commonly used interface for disk drives that was first completed in 1982. Unlike competing standards, SCSI is capable of supporting eight devices, or sixteen devices with Wide SCSI. However, with the SCSI host adapter located on ID number 07 and boots from the ID 00. This leaves the availability of six device connections. In the picture below, is an example of a SCSI adapter expansion card with an internal and external connection. Once installed in the computer this adapter would allow multiple SCSI devices to be installed in the computer. More advanced motherboard may also have available SCSI connections on the motherboard.

 USB

Short for Universal Serial Bus, USB (pronounced yoo-es-bee) is a plug and play interface that allows a computer to communicate with peripheral and other devices. USB-connected devices cover a broad range; anything from keyboards and mice, to music players and flash drives. For more information on these devices, see our USB devices section.

USB may also be used to send power to certain devices, such as smartphones and tablets, as well as charge their batteries. The first commercial release of the Universal Serial Bus (version 1.0) was in January of 1996.

Why is a scanner an input device?

A computer scanner is an input device because it takes information from the real world (e.g. a document or picture) and converts it into digital information for a computer to store or manipulate. A scanner is only able to send information to the computer and cannot receive information from the computer like a printer.

 

 

OUTPUT

PRINTER

A printer is a gadget that acknowledges content and realistic yield from a PC and exchanges the data to paper, for the most part to standard size sheets of paper. Printers shift in estimate, speed, modernity, and cost. When all is said in done, more costly printers are utilized for higher-determination shading printing.

PC printers can be recognized as effect or non-affect printers. Early effect printers worked something like a programmed , with a key striking an inked impact on paper for each printed character. The spot framework printer was a well known minimal effort PC printer. It's an effect printer that strikes the paper a line at any given moment. The best-known non-affect printers are the inkjet printer, of which a few makes of minimal effort shading printers are an illustration, and the laser printer. The inkjet splashes ink from an ink cartridge at short proximity to the paper as it moves by. The laser printer utilizes a laser shaft reflected from a mirror to draw in ink (called toner ) to chose paper territories as a sheet moves over a drum. 

The four printer characteristics of most enthusiasm to most clients are:

Shading: Colour is critical for clients who need to print pages for introductions or maps and different pages where shading is a piece of the data. Shading printers can likewise be set to print just in high contrast. Shading printers are more costly to work since they utilize two ink cartridges (one shading and one dark ink) that should be supplanted after a specific number of pages. Clients who don't have a particular requirement for shading and who print a considerable measure of pages will locate a high contrast printer less expensive to work. 

Determination: Printer determination (the sharpness of content and pictures on paper) is generally measured in spots per inch (dpi). Most cheap printers give adequate determination to most purposes at 600 dpi.

Speed: If you do much printing, the speed of the printer ends up noticeably essential. Reasonable printers print just around 3 to 6 sheets for each moment. Shading printing is slower. More costly printers are considerably quicker.

Memory: Most printers accompany a little measure of memory (for instance, one megabyte) that can be extended by the client. Having more than the base measure of memory is useful and quicker when printing out pages with expansive pictures or tables with lines around them (which the printer regards as a vast picture). 

Printer I/O Interfaces

The most widely recognized I/O interface for printers has been the parallel Centronics interface with a 36-stick plug. Later on, be that as it may, new printers and PCs are probably going to utilize a serial interface, particularly Universal Serial Bus or FireWire with a littler and less bulky attachment.

Printer Languages

Printer dialects are charges from the PC to the printer to advise the printer how to arrange the record being printed. These summons oversee text dimension, designs, pressure of information sent to the printer, shading, and so on. The two most well known printer dialects are Postscript and Printer Control Language.

Postscript is a printer dialect that utilizations English expressions and automatic developments to depict the presence of a printed page to the printer. This printer dialect was produced by Adobe in 1985. It presented new highlights, for example, layout text styles and vector designs. Printers now originate from the manufacturing plant with or can be stacked with Postscript bolster. Postscript is not confined to printers. It can be utilized with any gadget that makes a picture utilizing spots, for example, screen shows, slide recorders, and picture setters.

PCL (Printer Command Language) is an escape code dialect used to send summons to the printer for printing reports. Escape code dialect is supposed on the grounds that the escape key starts the charge grouping took after by a progression of code numbers. Hewlett Packard initially formulated PCL for spot network and inkjet printers. Since its presentation, it has turned into an industry standard. Different producers who offer HP clones have replicated it. Some of these clones are great, yet there are little contrasts in the way they print a page contrasted with genuine HP printers. In 1984, the first HP Laserjet printer was presented utilizing PCL. PCL helped change the presence of ease printer records from poor to excellent quality.

Text styles

 A text style is an arrangement of characters of a particular style and size inside a general typeface outline. Printers utilize inhabitant text styles and delicate textual styles to print records. Occupant textual styles are incorporated with the equipment of a printer. They are likewise called inner textual styles or inherent textual styles. All printers accompany at least one occupant text styles. Extra textual styles can be included by embeddings a textual style cartridge into the printer or introducing delicate textual styles to the hard drive. Inhabitant textual styles can't be deleted not at all like delicate text styles. Delicate text styles are introduced onto the hard drive and after that sent to the PC's memory when a report is printed that uses the specific delicate textual style. Delicate text styles can be bought in stores or downloaded from the Internet.

There are two sorts of text styles utilized by the printer and screen show, bitmap textual styles and diagram textual styles. Bitmap text styles are advanced portrayals of textual styles that are not adaptable. This implies they have a set size or a constrained arrangement of sizes. For instance, if an archive utilizing a bitmap text style measured to 24 point is sent to the printer and there is not a bitmap textual style of that size, the PC will endeavor to figure the correct size. This outcomes in the content watching extended or squashed. Rough edges are likewise an issue with bitmap text styles. Diagram text styles are numerical portrayals of the textual style that are sent to the printer. The printer at that point rasterizes (see raster designs) or changes over them to the specks that are imprinted on the paper. Since they are numerical, they are versatile. This implies the span of the textual style can be changed without losing the sharpness or determination of the printed content. TrueType and Type 1 textual styles are diagram text styles. Blueprint textual styles are utilized with Postscript and PCL printer dialects.

 

Convenience

One of the key advantages of printing out material is that it is convenient. If you need to mark it up or make notes on it, it is easy to do. Most printed documents are lighter and, when folded, smaller than a tablet or notebook computer. They are also easily replaced, so losing them or getting them wet isn't a major concern.

 Secure Delivery

Paper records can be anonymously delivered. Emailing a document creates a chain that shows who sent it, when they sent it and to whom they sent it. Once someone prints out a document, on the other hand, they can deliver it or not deliver it to anyone without creating a record of the delivery. This can be useful if you need to send information without having someone intercept it or without creating a record that you sent it.

 Ease of Reading

For many people, printed documents remain easier to read. The text on a printed document is, as of 2012, sharper than the sharpest display. While the iPad 3's display renders text with 264 dots per inch, even inexpensive printers can output 600 dots per inch. Most tablet and computer displays are backlit and glossy. This makes them prone to washing out in direct sunlight and prone to glare. The printed page, on the other hand, is easy to read in anything but dark conditions.

Enable to get computer output

Enables us to get computer output on paper. It is one of the most popular computer output      devices we often use to get information on paper - called hard copy.

  
MONITOR

Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

There are two kinds of viewing screen used for monitors.

    -Cathode-Ray Tube (CRT)

    -Flat-Panel Display

Cathode-Ray Tube (CRT) Monitor

The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

CRT Monitor

A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

There are some disadvantages of CRT −

Large in Size

High power consumption

The advantages of CRT

CRT, short for Cathode Ray Tube, is a technology commonly used in television sets and computer monitors. While perhaps not as popular as they once were, CRT monitors still offer many advantages over their main competitors. While they're bigger and bulkier than LCD monitors, many feel that the advantages still outweigh those of LCD displays.

While LCD picture quality is typically less than that of a CRT display, this is rapidly changing. LCD technology is advancing much quicker than CRT technology, meaning it's catching up to the CRT pictures quality. While these high-quality LCD monitors are costly and rare, as the technology advances they'll become cheaper and more readily available, meaning many of the CRT advantages will eventually be better on LCD screens.

Flat-Panel Display Monitor

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.

Flat Monitor

The flat-panel display is divided into two categories −

    Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).

    Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device).

 

The advantages of flat -panel display monitor

The flat panel monitor is stylish, space-saving and has low power requirements. With the advances in technology it has a better picture quality, gives maximum image size in the minimal space and is now very affordable. The monitors come in a variety of sizes, ranging from fourteen inches to thirty inches, to suit every requirement. Being lighter in weight than its predecessor, the CRT monitor, it is easily portable.

The smaller size monitors are ideal for normal daily tasks in a home. The larger sizes are designed to deliver clear displays to improve the entertainment and gaming experience. Therefore, there is a size that fits the need and budget of all users.