Computer devices and device drivers

In general, if we agree that the computer system is comprised of a computer case, monitor, keyboard, and mouse, as shown in Figure 3.1, then computer devices are organized into internal, external, peripheral, and network devices:

• An internal device is any device that is located in the computer's case. Examples of a computer's internal devices are the power supply, motherboard and accompanying components, hard drives, extension cards, and other internal hardware components that constitute the core computer architecture (that is everything inside a computer case).
• An external device is any device that is attached or connected to a computer's case, and as such constitutes the whole computer system. Examples of a computer's external devices are the keyboard, monitor, mouse, speakers, earphones, webcam, microphone, and other external hardware components.
• A peripheral device is considered to be any device that is geographically located near to the computer, and as such is not an essential part of the computer system as a whole. Examples of peripheral devices are printers, scanners, projectors, plotters, and other peripheral devices.
• A network device is actually a peripheral device connected to a computer over a network cable. Examples of network devices are network printers, network scanners, network backup libraries, Network Attached Storage (NAS), Storage Area Network (SAN), and other network devices.

Figure 3.1. The computer

Another categorization of computer devices are input and output devices. These devices either create input or output for the computer core architecture. Lately, with the advancement of technology, there are devices that act as an input and output device at the same time. Touch-enabled devices are an example of both input/output devices.

Note that, in today's literature, often external devices are referred to as peripheral devices too because these devices are connected to a computer case to add functionality. This perspective brings us to the conclusion that almost any device that resides outside of the core computer architecture is considered to be a peripheral device.

A device driver is a program that acts as a translator between computer hardware and an operating system. So, an OS operates the computer hardware by way of device drivers. Usually, the device drivers come with a DVD disk accompanying the device or can be downloaded from the manufacturer's website. However, there will often be no device driver accompanying the device, since nowadays, devices are PnP. PnP is explained in the Explaining PnP, IRQ, interrupts, and driver signing section of this chapter.