BIOS is a firmware code that a PC runs at start up to identify and initiate component hardware. This enables the PC to allow software programs to load, execute, and run for user use. More commonly known as booting up, BIOS simply enables a computer to work for the user in a capacity that is expected. It is referred to as memory only because it usually resides embedded within chips which use ROM as a main memory function. Part of the non-volatile memory formats, BIOS is not lost due to power loss or shut down.

In the beginning, BIOS chips could not be altered because of their placement on ROM and PROM memory. Then, the BIOS moved to EEPROM and flash, giving it more functionality than had been previously seen. The EEPROM gave the user the ability to easily change and update the BIOS. Manufactures issued updates to help users improve compatibility and remove bugs that were often troublesome to the applications in question concerning the BIOS in the same manner that updates are offered for many applications and hardware components of a PC. Since the issuance of these updates ran the risk of destroying a computer if the updates were interrupted by the user or otherwise, manufacturers altered the BIOS to include a block that must run separately and be upgraded before the rest of the blocks. This fix seems to have reduced the risk to computers while upgrading BIOS nicely.

As BIOS is flash-based, it shares the same risks that other flash-based memory experiences. Flash can only be rewritten a finite number of times before becoming unusable. Flash-burn viruses that occur after too many rewrites on the flash device will result in permanent corruption and the BIOS will be unable to be salvaged. The only true way to avoid having this happen is to replace the flash driven BIOS with a ROM based BIOS.

While some older, less sophisticated operating systems accessed the BIOS chips within the personal computer directly, more advanced systems access the BIOS indirectly. The main reason is that it is inefficient with today's more complex and faster technologies. Accessing the BIOS directly can seriously delay speeds which are valued in today's business and personal worlds.

If a process in the boot series of execution occurs from BIOS due to a forgotten disk in left in the hard drive, a user will get an error message. The message may vary from operating system to operating system, but all error messages will have one common fix. Simply remove the forgotten disk from the hard drive and reattempt your boot. The reason for this is that BIOS can accidentally attempt to boot your computer from incorrect files if such an occurrence as a forgotten disk is present. By removing the interfering disk, such as a floppy or installable application disk in your hard drive, and rebooting the computer after removal of the offending software, BIOS can continue the process without confusion.

No computer can run without BIOS. It is an integral part of unseen system checks that occur when the computer is started. If the system cannot check itself for possible problems and have its commands properly executed by BIOS, then the computer will halt booting executions. Based on this, and the knowledge that BIOS is generally flash based (although it can be ROM based), if your computer refuses to start, you may want to have your BIOS chips examined by a professional.