BIOS
/ˈbaɪ.ɒs/ · Noun · Development · Origin: 1975
Definitions
BIOS, or Basic Input/Output System, is firmware stored on a chip on the computer's motherboard that initializes and tests hardware components during the boot process and provides runtime services for operating systems and programs. When a computer powers on, the BIOS performs the POST (Power-On Self-Test) to verify that essential hardware like RAM, CPU, keyboard, and storage devices are functioning correctly. It then locates and loads the bootloader from a configured boot device to start the operating system. The BIOS also provides a setup utility (typically accessed by pressing Delete, F2, or F12 during boot) for configuring hardware settings like boot order, CPU clock speeds, and memory timings. BIOS was the standard firmware interface for IBM PC-compatible computers from 1981 through the 2010s, when it was largely replaced by UEFI (Unified Extensible Firmware Interface). Limitations of legacy BIOS include 16-bit real mode operation, a maximum bootable disk size of 2.2 TB (MBR partition scheme), and a text-based configuration interface.
In plain English: The very first software that runs when you turn on a PC. It checks that all the hardware is working, then finds and starts your operating system. You sometimes see its screen when mashing keys during startup.
Example: "Hit F2 during boot to enter the BIOS and change the boot order — otherwise it keeps trying to PXE boot off the network."
Origin Story
The Basic Input/Output System that boots your computer before the OS loads
Gary Kildall coined the term **BIOS** (Basic Input/Output System) for his CP/M operating system in 1975. The BIOS was the layer that abstracted hardware differences -- the same CP/M could run on different machines by swapping only the BIOS.
When IBM designed the PC in 1981, they adopted the concept. The IBM PC BIOS was stored in ROM and was the first code executed when the computer powered on. It performed the **POST** (Power-On Self-Test), initialized hardware, and loaded the operating system from disk.
The IBM PC BIOS was reverse-engineered by companies like Compaq and Phoenix, enabling the clone PC industry that made personal computers affordable. BIOS itself was eventually replaced by **UEFI** (Unified Extensible Firmware Interface), though people still call it "the BIOS."
Coined by: Gary Kildall
Context: CP/M, 1975
Fun fact: The legend goes that IBM tried to license CP/M for the PC, but Kildall went flying instead of meeting with IBM. This likely apocryphal story supposedly led IBM to license DOS from Microsoft instead, changing computing history forever.