After processing, a computer needs to act on the result of processing. This requires some kind of “output” device. There is a variety of output devices, this section will be subdivided based on the type of output.
The primary output device for real-time display is a computer monitor. A computer monitor is often connected to a computer via a VGA (video graphics adapter) port or a DVI (digital video interface) port. More modern computers use DVI ports. However, most monitors have both VGA and DVI ports for backward compatibility.
For “off-line”, the most common output device is a printer. There is a large variety of printers for different jobs. Inexpensive ink-jet printers can print text and color graphics, but the operating cost can be quite high. Professional ink-jet printers are mostly for photo-quality prints. Monochrome laser printers still account for most business printing due to the low operating cost. However, color laser printers are slowly becoming more popular as the cost drops. As a more recent development, solid-ink printers promise an operating cost that is even lower than that of color laser printers.
Multimedia applications often utilize audio output. Most modern computers come with the ability to produce audio signals that are suitable for amplified speakers.
Although real-time or off-line human output is common, many computer applications run in “batch” mode. Such applications often produce an output that is intended for computers.
For example, a computer system can store the processed information back onto its storage subsystem. In this case, the storage subsystem becomes an output device. Other times, the processed information is transmitted via networking to other computers, making the NIC an output device.
Embedded systems utilize a range of output devices to accomplish their objectives. For instance, an antilock brake system sends electrical pulses to a valve to control the clamping force exerted onto the calipers.
Because most (if not all) modern computers are electronic, the output of an embedded system is often electrical in nature. Such an output signal serves as the input of some output device that converts the electrical signal to a useful form.
For example, a manufacturering system has electrically controled air valves that control pneumatic components. A firework control system, on the other hand, uses the electrical signal to ignite fireworks.
It suffices to say that the range of output devices that can interface to a computer is very wide, and it expands on a daily basis.