Computer Hardware:
     • Tools, Static & Cleaning
     • Form Factor
     • PC Case & Fans
     • Motherboard
     • Processor (CPU)
     • Power Supply Unit
     • RAM
     • Hard Drive
     • Solid State Drive
     • Optical Drive
     • Floppy Disk Drive
     • Graphics Card
     • Sound Card
     • Network Card
     • Computer Monitor
     • Keyboard & Mouse
     • Laptop / Netbook
     • Building a Computer
     • Overclocking

Operating System & Backup:
     • Operating System
     • Drivers
     • Windows Tools
     • User Accounts
     • Backup
     • Windows 10

Internet & Network:
     • Internet
     • Wi-fi or Cable
     • Improve Broadband Speed
     • Network Computers

Computer Peripherals:
     • Printer
     • Scanner
     • External Hard Drive
     • USB Flash Drive

Computer Security:
     • Anti-virus
     • Anti-Spyware
     • Phishing
     • Firewall

Common PC Problems:
     • Slow Computer
     • Hardware Failure
     • Software Failure
     • Printing Problems

     • Windows Shortcuts
     • Glossary of Terms
     • HTML Colour Picker
     • Number Base Converter


The BIOS (Binary Input/Output System) is contained on a small EEPROM chip on the motherboard. The BIOS software is the first thing that is run when you switch on a computer. Its purpose is to initialise and test all system hardware components and then to load the operating system.

The CMOS contains the BIOS configuration data which you can change on the CMOS setup page. You can access the CMOS setup page by rebooting your computer and pressing a certain key in one second intervals during the initial start-up sequence (sometimes ‘DEL’, ‘ESC’, F1, or F2 etc).

BIOS chip & CMOS battery. 3V CMOS battery.
3V CMOS battery

When a computer is first turned on , the BIOS will perform a Power-On Self-Test (POST) and you may see the monitor display a memory count, and hard drive information etc before the operating system is loaded.

The CMOS (Complimentary Metal Oxide Semiconductor) is another component on the motherboard and is powered by a CMOS battery. CMOS contains the BIOS configuration data which can be accessed and configured via the CMOS setup page. This configuration data includes instructions on drive configuration, boot sequence, power management, and system time & date etc. It may also include settings for overclocking.

CMOS Setup page.
CMOS Setup Page

If the CMOS battery dies then the configuration data for the BIOS will be reset back to default settings. You will notice that the date and time will reset and it may even prevent the computer from booting correctly. Installing a new battery and reconfiguring the CMOS settings will fix this problem.

The BIOS itself can be rewritten and this is called ‘flashing’ or ‘flashing the BIOS’ . You might want to do this because a newer version is released by the BIOS manufacturer to fix bugs, or improve performance, or support newer hardware or even to fix a damaged BIOS. Flashing the BIOS used to be a little risky as an improperly executed or aborted BIOS update could make the motherboard unusable however newer motherboards may have a backup BIOS or will only rewrite the BIOS once a checksum is verified to confirm that the software is intact.


The Unified Extensible Firmware Interface (UEFI) is found on newer computers and is intended to replace the Basic Input/Output System (BIOS) interface.

UEFI is designed to improve software interoperability and address limitations of BIOS. Some advantages of UEFI firmware include:

•Better security by helping to protect the pre-start-up – or pre-boot – process against bootkit attacks.

•Faster start-up times and resuming from hibernation.

•Support for drives larger than 2.2 terabytes (TB).

•Support for modern, 64-bit firmware device drivers that the system can use to address more than 17.2 billion gigabytes (GB) of memory during start-up.

•Capability to use BIOS with UEFI hardware.

Note that a newer computer which has UEFI uses a new partition style called GPT (GUID Partition Table) on its storage device (Hard Drive etc) but can also use the older MBR (Master Boot Record) partition style by selecting 'Legacy Mode' in the UEFI (CMOS setup page).