BIOS

Summary

This ITFreeTraining lesson explains how BIOS helps a computer start, check its hardware, and hand off control to an operating system.

BIOS and firmware

BIOS (Basic Input/Output System) is motherboard firmware that provides basic hardware communication and startup functions. The lesson says BIOS originated with IBM in 1975 and was later reverse-engineered for non-IBM computers.

Startup sequence

Pressing the power button initiates a power-supply check. Once power reaches the CPU, BIOS code is copied into system memory so the CPU can execute it. A computer without memory cannot proceed and may signal an error with beeps.

POST and hardware checks

BIOS runs POST (Power-On Self-Test), checking components such as memory, storage, the keyboard, and pointing devices. It can also initialize add-on BIOS code, such as code on a RAID controller, to make attached storage bootable.

Errors and troubleshooting

BIOS may report problems with beep codes or on-screen messages. Beep codes vary between BIOS implementations. The lesson recommends checking that memory and the video card are seated properly when a computer beeps but displays nothing. Some errors, such as a missing keyboard, can be configured to be ignored.

Booting the operating system

BIOS checks devices in a configurable boot order, finds a bootable device, and loads its bootloader. The bootloader bridges the gap between BIOS’s basic capabilities and the operating system, which then loads.

BIOS after startup

The lesson describes traditional BIOS as 16-bit. Modern operating systems generally access hardware directly once loaded, so BIOS is mainly needed to initialize the system and start the boot process.

CMOS settings and battery

CMOS-related settings include boot order, date and time, and CPU and memory timings. A motherboard battery preserves these settings while the computer is off. If the battery fails, settings or the clock may reset.

UEFI compared with BIOS

UEFI is presented as BIOS’s successor. It can support different CPU architectures, including 32-bit and 64-bit operation, and boot from storage larger than 2 TB. UEFI often has a graphical interface, though it can also be text-based; BIOS can also have a graphical interface.

Guide and tutorial coverage

This is an introductory technical explainer covering BIOS operation, startup troubleshooting, CMOS settings, and UEFI. Although the introduction mentions BIOS upgrades, the supplied subtitles do not provide upgrade instructions. No product review is included.

Main speaker and source

A single instructional narrator from ITFreeTraining.