Monitor
You will interact with your computer largely through its monitor or video display. It works much like a television; some early computers used a TV. Because of its construction, the monitor is often known as a cathode ray tube, or CRT for short.
Monitors come in a variety of types and are generally described by these terms associated with video.
- Alphanumeric. A combination of letters and numbers.
- Graphic. The ability to display diagrams or pictures built up of individual dots.
- Pixel. A single dot on the monitor screen. The name comes from "picture element." Multiple pixels are used to form characters and graphics.
Color vs. Monochrome
Color mimics the world as we normally see it with different shades and hues in differing intensity. The various hues are typically associated with those found in a rainbow. On a computer system, because of its digital nature, the infinite variety of colors found in nature can only be simulated with a mix of discrete color values. The more of these the system can handle, the more the display will look "natural."
Monochrome is a single color (actually two: black & white or bright and dark).
Some of the terms you'll hear about the classes of microcomputer video are defined here:
- Monochrome: Original IBM-PC video. Character-based with no graphics capability. A third party enhancement called Hercules added graphics capability.
- CGA: IBM's first attempt at a color graphic standard. CGA is a low resolution standard, largely good for games.
- EGA: IBM's second attempt at a color graphic standard. At 640x350 dot resolution, EGA displayed graphics acceptably well but the dot count did not match the 4x3 aspect ratio of a typical monitor so software still could not draw a circle by plotting equal numbers of points on the screen.
- VGA: An IBM standard released with the PS/2. The 640x480 resolution is both good for graphics and has a one to one screen aspect ratio so circles can be drawn as circles. "Super" VGA resolution of 800x600 is also available.
Advanced resolutions (1024x768 and 1240x1024) are also available with higher resolutions leaving specialized labs soon.
Input Devices
Two input devices will be your primary interface with your computer: Keyboard & Mouse.
The keyboard is addressed in a separate tutorial.
Mouse
The mouse is a slightly different animal. The body of this device contains a ball which, when rolled along a desk or other flat object transmits position information to the computer. Buttons on the mouse activate various functions.
Position is obtained by various means. In some versions of the mouse you have to use a special pad with grid marks so that optical sensors can derive position information from the grid.
There are many other specialized input devices.
Output Devices
There are many output devices for your computer. Two to note are: Plotters & Printers.
A plotter is a device that uses some mechanism to drive pens in defined horizontal/vertical motions in order to produce combined text and graphics figures. Most are driven by software that not only controls pen motion, but also pen color, with different colors available depending on the model purchased.
Most personal computer plotters come with a flat bed. Other models are available with a pen that moves back and forth and wheels that drive the paper back and forth for the second dimension of motion. Finally, some few plotters move the pen back and forth and roll a drum with paper attached to obtain the other dimension.
Printers
By far, paper is the single largest output you will have from your computer. Despite claims for "paperless" offices, it is still rare to not see printers outputting reams of paper.
Modern printers come in a variety of types, with many capabilities.
One class is described as non-impact because the actual printing element never touches the paper. In the other class the print element does touch the paper, sometimes quite hard. Of course, it is named impact.
Let's categorize some printers:
| Impact | Non-Impact |
| Dot Matrix Characters made up of dots | Ink-jet Dots of ink make up characters |
| Daisy Wheel Single character impacts | Thermal Wires burn special paper |
| Line Printer Prints entire line at a time | Laser Full page printer |
Non-impact Printers
Thermal printers used to be popular, but their use of special paper that was subject to extraneous marking (not to mention cost). The use of thermal printers has dropped significantly.
Two others are popular: Ink-jet and laser.
Ink-jet
The ink jet printer "shoots" individual dots of ink to the paper, calculating the location of each dot in order to form individual characters or dot graphics. When using these, a good paper is necessary to avoid smearing.
Laser
The laser printer is noted for producing a page of text at a time. In this printer a laser scans a photoactive plate building up an image of the printed page. Like in a copy machine, the plate is dusted with toner which sticks to the exposed areas. Paper is then placed in contact with the plate, transferring the image to the paper. A final heat bonding seals the toner to the paper. This all takes just a few seconds.
Impact Printers
There are two impact printers you will likely see with a personal computer: Dot matrix Daisy wheel (or Thimble)
The difference between the two is in the quality of the output. Dot matrix printers form characters from individual dots whereas a daisy wheel printer imprints fully-formed characters, much like a typewriter.
The dot matrix is the more versatile of the two. Because of this the daisy wheel printer is not seen much any longer.
Both printers impact the paper through a ribbon to transfer ink to the paper by the hitting element. Dot matrix printers use 9 to 24 individual wires.
