BIOS and UEFI
Also known as: basic input/output system, Unified Extensible Firmware Interface, UEFI firmware
BIOS (basic input/output system) and its modern replacement, UEFI (Unified Extensible Firmware Interface), are small programs stored on a chip on the motherboard.
They run the instant you press the power button, check the hardware, and hand control to the operating system. Their settings menus control boot order, security features, and hardware options. While most people never need to open these settings, UEFI features such as Secure Boot quietly protect computers from malware that loads before Windows.
BIOS and UEFI, explained at three levels
At home
BIOS or UEFI is like a building's caretaker who arrives first each morning, turns on the lights, checks the doors, and then opens up for everyone else. Your operating system can't start without it.
At work
UEFI settings control security features that protect company computers before Windows even starts.
At home
You can usually enter UEFI settings by pressing a key such as F2, F10, F12, or Delete while the computer starts. It's where you change boot order to start from a USB drive.
At work
UEFI supports Secure Boot, large drives with GPT partitions, faster startup, and network booting. Firmware updates from manufacturers fix security flaws and hardware bugs and should be part of patching.
At home
Updating firmware is usually safe through Windows Update or the maker's tool, but a power cut midway can break a computer. In my opinion, plug in laptops before any firmware update.
At work
Manage firmware settings centrally where vendor tools allow, set firmware passwords, keep Secure Boot enabled, track firmware versions in asset inventory, and plan for Secure Boot certificate updates. Firmware attacks such as bootkits survive operating system reinstalls.
Real-world examples
At home
Jerome wanted to install Linux from a USB stick. He pressed F12 at startup to open the boot menu and chose the USB drive instead of the hard drive.
At work
Sophie manages devices for a Regina nonprofit. She used the laptop maker's management tool to push a firmware update fixing a security flaw to all 80 laptops.
How it compares
| feature | BIOS | UEFI |
|---|---|---|
| Era | 1970s to 2010s | 2005 onward |
| Interface | Text, keyboard only | Often graphical, mouse support |
| Drive size limit | About 2 TB boot drives | Far larger |
| Secure Boot | No | Yes |
UEFI is the modern successor to BIOS, faster and more secure.
For analysts
I'd include firmware in patch management requirements. It's often missed, and vulnerabilities there can be harder to detect and fix than operating system flaws.
History & origin
Gary Kildall coined the term BIOS for his CP/M operating system in the mid-1970s, and the IBM PC in 1981 made it standard. Compaq's legally 'clean-room' recreation of the IBM BIOS in 1982 opened the door to PC clones, followed by firms such as Phoenix Technologies selling compatible versions. Intel developed EFI in the late 1990s for its Itanium servers, and the industry formed the UEFI Forum in 2005 to standardize it. Windows 8 in 2012 brought UEFI and Secure Boot to mainstream PCs, and Windows 11 in 2021 required UEFI with Secure Boot capability and a TPM 2.0 chip. Microsoft's original 2011 Secure Boot certificates began expiring in 2026, requiring updates to keep older PCs trusted. In my view, firmware is the most important software almost nobody thinks about.