Input and Output Devices

1. Input and Output Devices

2. Expansion slots, cards, and ports

3. How does a computer get data from RAM to a peripheral device? • Within a computer, data travels from one component to another over circuits called a data bus. One part of the data bus runs between RAM and the microprocessor. Another part of the data bus runs between RAM and various storage devices. That is called expansion bus.

4. What’s an expansion slot? • It’s a long, narrow socket on the motherboard into which you can plug an expansion card. • An expansion card is a small circuit board that provides a computer with the ability to control a storage device, an input device, or an output device. Expansion cards are also called “expansion boards”, “controller cards” or “adapters”. • Most desktop computers have four to eight expansion slots, but some of the slots usually contain expansion cards.

5. What are the major types of expansion slots? • ISA (Industry Standard Architecture) slots are an old technology, used today only for some modems and other relatively slow devices. • PCI (Peripheral Component Interconnect) slots offer fast transfer speeds and a 32-bit or 64-bit data bus. These slots typically house a graphics card, sound card, video capture card, modem, or network interface card. • AGP (Accelerated Graphics Port) slots provide a high-speed data pathway that is primarily used for graphics cards.

6. Do notebook computers also contain expansion slots? • Most notebook computers are equipped with a special type of external slot called a PCMCIA slot (Personal Computer Memory Card International association). Typically, a notebook computer has only one of these slots, but the slot can hold more than one PC card (also called “PCMCIA expansion cards” or “Card Bus Cards”).

7. What is an expansion port? • It is any connector that passes data in and out of a computer or peripheral device. Ports are sometimes called “jacks” or “connectors”. • An expansion port is often housed on an expansion card so that it is accessible through an opening in the back of the computer’s system unit.

8. What are the major types of expansion cables? • With so many types of ports, you can expect a corresponding variety of cables. If a cable is supplied with a peripheral device, you can usually figure out where to plug it in by matching the shape of the cable connector to the port. If you have to purchase a cable, you’ll need to know the correct type and designation.

9. Display Devices

10. What are the components of a typical computer display system? • The two key components of a computer display system include a graphics card and a display device, such as a monitor or LCD screen. • A graphics card (also called a “graphics board” or a “video card”) contains circuitry that generates the signals for displaying an image on screen. It also contains special video memory, which stores screen images as they are processed, before they are displayed.

11. What’s the difference between a CRT and an LCD? • The advantages of an LCD (liquid crystal display) monitor include display clarity, low radiation emission, portability and compactness. Unfortunately, it can be triple the price of an equivalent CRT (Cathode Ray Tube) and they have a limited viewing angle.

12. Which display device produces the best image? • Image quality is a factor of screen size, dot pitch, resolution, and color depth. Typical monitor screen sizes range from 13” to 21”. Dot pitch is a measure of image clarity. Resolution is the number of horizontal and vertical pixels that are displayed on the screen. The number of color that a monitor and graphics card can display is referred to as color depth.

13. What about notebook computer display system? • A passive matrix screen relies on timing to make sure the liquid crystal cells are illuminated. As a result, the process of updating the screen image does not always keep up with moving images, and the display can appear blurred. Newer notebooks feature an active matrix screen, sometimes referred to as “TFT” (thin film transistor), which updates rapidly and is essential for a crisp display of animations and video.In the world of notebook computers, SVGA (Super video graphics array) usually means 800X600 resolution. XGA (extended graphics array) usually means 1024X768 resolution.

14. Printers

15. What features should I look for in a printer? • Today’s printer technologies include ink jet, solid ink, thermal transfer, dye sublimation laser and dot matrix. • Resolution: The quality or sharpness of printed images and text depends on the printer’s resolution-the density of the grid work of dots that create an image. At normal reading distance, a resolution of about 900 dpi (dots per inch) are ok. • Print speed: is measured either by pages per minute (ppm) or characters per second (cps).

16. What’s the most popular type of printer? • The ink jet printers are the more inexpensive and have a good quality. • Today’s ink jet printers have excellent resolution, which can range from 600 dpi to 2880 dpi, depending on the model.

17. What’s the difference between an ink jet printer and a solid ink printer? • A solid ink printer melts sticks of crayon-like ink and then sprays the liquefied ink through the print head’s tiny nozzles. The ink solidifies before it can be absorbed by the paper, and a pair of rollers finishes fusing the ink onto the paper. • An ink jet printer has a nozzle-like print head that sprays ink onto paper to form characters and graphics.

18. What about thermal wax transfer and dye sublimation printers? • A thermal wax transfer printer uses a page-sized ribbon that is coated with cyan, magenta, yellow, and black wax. The print head consists of thousands of tiny heating elements that melt the wax onto specially coated paper or transparency film. • A dye sublimation printer is very similar to the thermal wax transfer printer, but the page-sized ribbon contains dye instead of colored wax.

19. Is a laser better than an ink jet? • A laser printer uses the same technology as a photocopier to paint dots of light on a light-sensitive drum. Electrostatically charged ink is applied to the drum, then transferred to paper. • Personal laser printers produce six to eight ppm (pages per minute) at a resolution of 600 dpi.

20. Why would anyone want a dot matrix printer? • A dot matrix printer produces characters and graphics by using a grid of fine wires. • With a resolution of 140 dpi, a dot matrix printer produces low-quality output with clearly discernible dots forming letter and graphics. • A fast dot matrix device can print at speeds up to 455 cps-about 5 pages per minute.