Floppy Disk

                 Some older computers provide drives for magnetic diskettes that are 5.25 inches square, about 1 millimeter thick, and capable of holding 1.2 megabytes of data. These were sometimes called "floppy disks" or "floppies" because their housings are flexible. In recent years, 5.25-inch diskettes have been largely replaced by 3.5-inch diskettes, which are physically more rugged. Many people also call the newer hard-cased diskette a "floppy."

                    Magnetic diskettes are convenient for storing individual files and small programs. However, the magneto-optical (MO) disk is more popular for mass storage, backup, and archiving. An MO diskette is only a little larger, physically,than a conventional 3.5-inch magnetic diskette. But because of the sophisticated read/write technology, the MO diskette can store many times more data.

Speakers

Computer speakers, or multimedia speakers, are speakers external to a computer, that disable the lower fidelity built-in speaker. They often have a low-power internal amplifier. The standard audio connection is a 3.5 mm (approximately 1/8 inch) stereo jack plug often color-coded lime green (following the PC 99 standard) for computer sound cards. A plug and socket for a two-wire (signal and ground) coaxial cable that is widely used to connect analog audio and video components. Rows of RCA sockets are found on the backs of stereo amplifier and numerous A/V products. The prong is 1/8" thick by 5/16" long. A few use an RCA connector for input. There are also USB speakers which are powered from the 5 volts at 500 milliamps provided by the USB port, allowing about 2.5 watts of output power.

Computer speakers range widely in quality and in price. The computer speakers typically packaged with computer systems are small, plastic, and have mediocre sound quality. Some computer speakers have equalization features such as bass and treble controls.

The internal amplifiers require an external power source, usually an AC adapter. More sophisticated computer speakers can have a subwoofer unit, to enhance bass output, and these units usually include the power amplifiers both for the bass speaker, and the small satellite speakers.

Inkjet Printer

                 An inkjet printer is a computer peripheral that produces hard copy by spraying ink onto paper. A typical inkjet printer can produce copy with a resolution of at least 300 dots per inch ( dpi ). Some inkjet printers can make full color hard copies at 600 dpi or more. Many models include other devices such as ascanner , photocopier , and dedicated fax machine along with the printer in a single box.

               In the inkjet printing mechanism, the print head has several tiny nozzles, also called jets. As the paper moves past the print head, the nozzles spray ink onto it, forming the characters and images. An inkjet printer can produce from 100 to several hundred pages, depending on the nature of the hard copy, before the ink cartridges must be replaced. There is usually one black ink cartridge and one so-called color cartridge containing ink in primary pigments (cyan, magenta, and yellow). Some inkjet printers use a single cartridge with cyan, magenta, yellow, and black ink. A few models require separate cartridges for each primary pigment, along with a black ink cartridge.

                The principal advantage of inkjet printers is the fact that most of them are inexpensive. Inkjet printers are often given away at computer superstores along with the purchase of a personal computer or substantial peripheral. Even the cheapest inkjet printers are satisfactory for most of the needs of personal computer users. High-end inkjet printers can render digital images on special paper, with quality rivaling that of professionally produced glossy or matte photographs. Another advantage of inkjet printers is their light weight and modest desktop footprint . Many models are easy to transport, and are preferred by traveling salespeople for this reason alone.

Laser Printer

                      A laser printer is a popular type of personal computer printer that uses a non-impact (keys don't strike the paper), photocopier technology. When a document is sent to the printer, a laser beam "draws" the document on a selenium-coated drum using electrical charges. After the drum is charged, it is rolled in toner, a dry powder type of ink. The toner adheres to the charged image on the drum. The toner is transferred onto a piece of paper and fused to the paper with heat and pressure. After the document is printed, the electrical charge is removed from the drum and the excess toner is collected. Most laser printers print only in monochrome. A color laser printer is up to 10 times more expensive than a monochrome laser printer.

                         IBM introduced the first laser printer in 1975 for use with its mainframecomputers. In 1984, Hewlett-Packard revolutionized laser-printing technology with its first LaserJet, a compact, fast, and reliable printer that personal computer users could afford. Since then, laser printers have decreased further in price and increased in quality. Hewlett Packard continues to be the leading manufacturer with competitors including Lexmark, Okidata, and Xerox.

The laser printer is different from an inkjet printer in a number of ways. The toner or ink in a laser printer is dry. In an inkjet, it is wet. Over time, an inkjet printer is about ten times more expensive to operate than a laser printer because ink needs replenishing more frequently. The printed paper from an inkjet printer will smear if wet, but a laser-printed document will not. Both types of printer operate quietly and allow fonts to be added by using font cartridges or installing soft fonts. If your printing needs are minimal, an inkjet printer is sufficient. But if your printing volume is high, consider buying a laser printer.

When buying a laser printer, these are some important features to consider:

Print capacity and speed: 

                    Personal laser printers are sufficient for printing an average of 200 pages per week. These are low-end and cost $200 and up. They can print up to eight ppm (pages per minute). A workgroup printer is needed if an average of 1000 pages per week is needed. These print up to 24 ppm and cost $1000 to $6000 and more. Production printers are needed for printing 50,000 or more pages per week. These are quite expensive and are used by commercial publishers. They can print up to 700 ppm and cost $100,000 and up. They can print 24 hours a day, seven days a week.

Resolution:

                  The standard resolution in most laser printers today is 600 dots-per-inch ( dpi ). This resolution is sufficient for normal everyday printing including small desktop publishing jobs. A high-end production printer might have a resolution of 2400 dpi. Some laser printers still use a resolution of 300 dpi. This resolution can cause jagged lines to appear on the outer edge of an image. Hewlett Packard created RET (Resolution Enhancement Technology) to correct this. RET inserts smaller dots at the edges of lines and to smooth the rough edges. RET does not improve the resolution, but the document looks better. If you purchase a printer with 300 dpi, make sure it has RET.

Printer

                In computers, a printer is a device that accepts text and graphic output from a computer and transfers the information to paper, usually to standard size sheets of paper. Printers are sometimes sold with computers, but more frequently are purchased separately. Printers vary in size, speed, sophistication, and cost. In general, more expensive printers are used for higher-resolution color printing.

                       Personal computer printers can be distinguished as impact or non-impactprinters. Early impact printers worked something like an automatic typewriter, with a key striking an inked impression on paper for each printed character . The dot-matrix printer was a popular low-cost personal computer printer. It's an impact printer that strikes the paper a line at a time. The best-known non-impact printers are the inkjet printer, of which several makes of low-cost color printers are an example, and the laser printer . The inkjet sprays ink from an ink cartridge at very close range to the paper as it rolls by. The laser printer uses a laser beam reflected from a mirror to attract ink (called toner ) to selected paper areas as a sheet rolls over a drum.

The four printer qualities of most interest to most users are:

• Color: Color is important for users who need to print pages for presentations or maps and other pages where color is part of the information. Color printers can also be set to print only in black-and-white. Color printers are more expensive to operate since they use two ink cartridges (one color and one black ink) that need to be replaced after a certain number of pages. Users who don't have a specific need for color and who print a lot of pages will find a black-and-white printer cheaper to operate.
• Resolution: Printer resolution (the sharpness of text and images on paper) is usually measured in dots per inch. Most inexpensive printers provide sufficient resolution for most purposes at 600 dpi.
• Speed: If you do much printing, the speed of the printer becomes important. Inexpensive printers print only about 3 to 6 sheets per minute. Color printing is slower. More expensive printers are much faster.
• Memory: Most printers come with a small amount of memory (for example, one megabyte ) that can be expanded by the user. Having more than the minimum amount of memory is helpful and faster when printing out pages with large images or tables with lines around them (which the printer treats as a large image).

Printer I/O Interfaces

The most common I/O interface for printers has been the parallel Centronics interface with a 36- pin plug. In the future, however, new printers and computers are likely to use a serial interface, especially Universal Serial Bus or FireWire with a smaller and less cumbersome plug.

Printer Languages

                  Printer languages are commands from the computer to the printer to tell the printer how to format the document being printed. These commands manage font size, graphics, compression of data sent to the printer, color, etc. The two most popular printer languages are Postscript and Printer Control Language .

           Postscript is a printer language that uses English phrases and programmatic constructions to describe the appearance of a printed page to the printer. This printer language was developed by Adobe in 1985. It introduced new features such as outline font s andvector graphics . Printers now come from the factory with or can be loaded with Postscript support. Postscript is not restricted to printers. It can be used with any device that creates an image using dots such as screen displays, slide recorders, and image setters.

            PCL (Printer Command Language) is an escape code language used to send commands to the printer for printing documents. Escape code language is so-called because the escape key begins the command sequence followed by a series of code numbers. Hewlett Packard originally devised PCL for dot matrix and inkjet printers. Since its introduction, it has become an industry standard. Other manufacturers who sell HP clones have copied it. Some of these clones are very good, but there are small differences in the way they print a page compared to real HP printers. In 1984, the original HP Laserjet printer was introduced using PCL. PCL helped change the appearance of low-cost printer documents from poor to exceptional quality.

Fonts

              A font is a set of characters of a specific style and size within an overall typeface design. Printers use resident fonts and soft fonts to print documents. Resident fonts are built into the hardware of a printer. They are also called internal fonts or built-in fonts. All printers come with one or more resident fonts. Additional fonts can be added by inserting a font cartridge into the printer or installing soft fonts to the hard drive. Resident fonts cannot be erased unlike soft fonts. Soft fonts are installed onto the hard drive and then sent to the computer's memory when a document is printed that uses the particular soft font. Soft fonts can be purchased in stores or downloaded from the Internet.

Monitor

A monitor is the screen on which words, numbers, and graphics can be seem.  The monitor is the most common output device.

                    In computers, a monitor is a computer display and related parts packaged in a physical unit that is separate from other parts of the computer. Notebook computers don't have monitors because all the display and related parts are integrated into the same physical unit with the rest of the computer. In practice, the terms monitor and display are used interchangably.

Scanner

                A scanner is a device that images a printed page or graphic by digitizing it, producing an image made of tiny pixels of different brightness and color values which are represented numerically and sent to the computer. Scanners scan graphics, but they can also scan pages of text which are then run through OCR (Optical Character Recognition) software that identifies the individual letter shapes and creates a text file of the page's contents.