Firmware Overview

Firmware represents a middle ground between hardware and software. Like hardware, firmware is physical: a chip or chips attached to devices such as motherboards, video cards, network cards, modems, and printers. However, firmware is also software: Firmware chips (such as the motherboard BIOS) contain instructions for hardware testing, hardware configuration, and input/output routines. In essence, firmware is "software on a chip," and the software's job is to control the device to which the chip is connected.

Because firmware works with both hardware and software, changes in either one can cause firmware to become outdated. Outdated firmware can lead to device or system failure or even data loss.

Until the mid-1990s, the only way to change firmware was to remove the chip and replace it with one containing new instructions. Most firmware today is flashable , meaning that its contents can be changed through software. You'll learn more about the most common type of firmware, the motherboard BIOS, in Chapter 6, "BIOS and CMOS Configuration."