Understanding Computer Output Devices and Printing Technology

Output Devices

Dot Matrix Printers

Dot matrix printers are known for their ability to handle continuous forms and harsh environments.

Advantages

• Can print long jobs.
• Inexpensive to maintain.
• Can work in dirty atmospheres.
• Can print different characters.

Disadvantages

• Expensive to purchase.
• Noisy operation.
• Poor quality printing.

Inkjet Printers

Inkjet printers are made up of a print head, ink cartridge, motor, and paper feed mechanism.

General Printer Operation

The following steps describe how a typical printer processes a job:

1. Data is sent to the printer driver via USB.
2. The data is converted into a form the printer understands.
3. The system checks whether the job is able to be printed.
4. The printer receives data in the printer buffer (temporary memory), allowing the computer to perform other tasks while printing.
5. The print cleaning process initiates.
6. The paper feed is activated.
7. Paper moves into the correct position.
8. The print head/mechanism passes through the paper and prints the text.
9. Once the printer buffer is empty, an interrupt signal is sent, indicating the job is finished.

Inkjet Printer Pros and Cons

Advantages

• Cheap to purchase.
• High quality output.

Disadvantages

• Ink cartridges do not last long.
• Printing can smudge if touched.

Laser Printers

Laser printers utilize a printing drum with a positive charge. As the drum rotates, the laser passes through, creating electrostatic images. Toner (ink) only sticks to the negatively charged parts of the drum. Finally, the paper goes through a fuser, which melts the toner onto the paper.

Laser Printer Pros and Cons

Advantages

• Low noise operation.
• Cartridges last a very long time.

Disadvantages

• Maintenance and running costs are high.
• They produce ozone.

3D Printers

3D printers break down the printing of the object into layers.

Common Uses of Printers

• 3D Printers: Creation of museum artifacts and production of car parts.
• Dot Matrix Printers: Salary slips and continuous paper forms.
• Inkjet Printers: High quality printing (photos, documents).
• Laser Printers: High speed printing of high volume documents.

Display Technologies (Monitors)

Cathode Ray Tube (CRT) Monitors

CRT monitors are known for their quality image reproduction.

Thin-Film Transistor (TFT) Displays

TFT displays are lightweight, consume little power, and offer increased flexibility.

Specialized Output Devices

2D and 3D Cutters

These devices are used to cut materials, such as glass, typically operating in a 2D direction.

Loudspeakers

Loudspeakers work via the following signal path:

Computer → DAC (Digital-to-Analog Converter) → Amplifier → Loudspeaker

Projection Systems

Digital Light Processing (DLP) Projectors

In DLP systems, a white light passes through the projector and filters to the chip, where the colors filter to produce an image, often utilizing grayscale technology.

Liquid Crystal Display (LCD) Projectors

A light beam is sent through the display. The light passes through, and its wavelength is changed depending on the pixels, combining the colors with grayscale information.