Ouput devices have only one purpose: to display (print or sound) the results of instructions and data entered by the user and processed by the PC.

The Monitor

     The primary component in the PC monitor is the cathode ray tube (CRT). On a color monitor, each dot carries one of three colors: red, green, and blue. Three dots, one of each color, are arranged together to create a pixel (short for picture element). Three electron beams illuminate a pixel's dots in varying degrees. This variation produces different color shadings. The following are a few terms used with monitors:
     The names of the technologies used to control the illumination of the CRT's phosphor sound are as follows:
     The number of and distance between pixels determines the quality of the images produced. The number of displayable pixels on a screen is the resolution. The more pixels available for display, the higher the resolution, which results in much better display.

     The distance between pixels is the dot pitch. The dot pitch is the distance in millimeters between dots of the same color in two adjacent pixels, but in effect, it is the distance between the pixels. Common dot pitch sizes are .39mm, .35mm, .28mm, and .25mm. The smaller the dot pitch, the better the picture quality. It also stands to reason that a smaller dot pitch makes room for more pixels, which improves the monitor's resolution.

     One final note on resolution: The higher the resolution, the smaller each pixel appears on the screen. If a the Windows icons are too small on a new monitor, lower the resolution.

The Video Adapter Card

     The video card, also called the graphics adapter, converts a graphics image from a software application into a series of instructions that tell the monitor's internal controller how to draw the image on the screen and what colors to use. The different video adapter cards are as follows:
The video card and monitor must use the same graphics standard to work properly.
Accelerated Video

     Virtually all modern video cards are accelerators, getting their abilities from their video chipset. An accelerated video card, sometimes called a Windows accelerator, has a video coprocessor that enables it to calculate many of the display calculations previously handled by the CPU. Accelerator cards allow the processor to issue commands rather than instructions. Accelerated video cards include a video coprocessor that offloads video image production from the CPU.

The Video Image Buffer

     Monochrome monitors display about 2K of data, and processors can afford to set asside a portion of system memory to hold it. As new technology developed and the size of the data grew, putting some memory on the video card is called video memory, or frame buffer.

     The first video memory was standard DRAM, which proved to be impractical because of its need to be continually refreshed. This impracticality led to the development of specialized video memory technologies:
     Graphics support is also integrated into some systemboards, using a unified memory architecture, named becuase it uses system RAM for video memory. This technology produces poorer graphics than memory on a video card.

Video Memory Size

     The memory on a video card must be sufficiently large so that it can hold an entire screen of data. Video memory must be large enough to store the entire digital bitmap produced by the processor. Video memory is usually sized as 256K, 512K, 1MB, 2MB, and so forth. Above 1MB, always jump to the next whole megabyte of video memory. Use the following procedure to calculate the amount of video memory needed:
  1. Multiply the resolution: 800 x 600 = 480,000
  2. Multiply 480,000 by the color bits: 480,000 x 8-bits = 3,840,000
  3. Divide 3,840,000 by 8 bits: 3,840,000 / 8 = 480,000
     When using 8-bit color schemes, you don't have to do the last two steps, however, if you were calculating the frame buffer for 16-bit color, you would multiply by 16 to get 7,680,000, then divide by 8 bits (the number of bits in a byte) to convert to bytes (960,000).

     Usually, a video card has a seperate software driver for each resolution or color depth, which is why you must reboot the PC after you change the display settings of your monitor in Windows.
The Connection

     The monitor connects to the system through a connector on the back of the adapter card or through a connector on the systemboard. The number of pins on the connector is somewhat indicative of the adapter's capabilities. The following are the different connectors for monitors:
Monitor Power and Safety

     Dust collects on the glass of the monitor, held there by static electricity that also builds up over time. Never clean the monitor's glass with any liquid solution while it's powered on. If you want to use a spray cleaner, turn off the monitor, spray a cloth, and then wipe the monitor. You can also find antistatic wipes that are made just for this purpose.

     In active mode, the monitor uses more power than the whole rest of the PC system. Reducing its power consumption in its idle states is a focus of the United States Environmental Protection Agency (EPA) program called Energy Star, or Green Star. The purpose of this program is to certify PCs and monitors that use less than 30 watts in all power modes and reduce their power consumption by 99 percent in sleep or suspend mode. PCs that meet this standard can display the Energy Star logo.

     The powerful electromagnetic forces in the monitor or any placed nearby can cause the internal components of the monitor to become magnetized. When this happens, the image resolution and color quality produced by the monitor can be distorted or faded, especially in the corners. A process called degaussing eliminates most of the magnetization inside the CRT. Most color monitors have a built-in degaussing protocol that can usually be accessed from the monitor's front panel. Degaussing a circuit too much can damage it.

Monitors meeting the Green standard must reduce their power consumption by 99 percent in suspend mode.

To be safe, send the monitor to the manufacturer to be fixed or to a salvage company to be disposed of properly.

If you must open the case to work on a monitor, do not wear an ESD grounding strap. Also, unplug the AC cord from the power source, and use the buddy system (never work alone on a monitor).

Never use a regular multimeter or other test equipment to measure the voltages on a monitor. The monitor has a large capacitor that holds a very large charge (+-20,000 Volts).
The Sound Card

     Essentially, three sound card standards have existed: the 8-bit AdLib, the higher-end SoundBlaster, and the General MIDI (musical instrument digital interface). Most of the sound cards in use today support both the SoundBlaster and General MIDI standards for recording and playback. The AdLib card has all but disappeared. Most sound cards are CD-quality, which means that they capture and reproduce digital audio at the same resolution (CD-A) used for audio CDs.

     CD-ROM drives produce sound through a phone jack on its face, or its sound can be piped through the sound card for broadcast to the PC's speakers. The audio cable of the CD-ROM is attached to the sound card.

SoundBlaster compatible sound cards, the current standard, are normally configured to support: The connectors found on virtually all sound cards are: