Basic Input/Output System
BIOS stands for Basic Input/Output System. The photo above shows an example of what a built in BIOS program looks like. BIOS programs vary from computer to computer, but every computer has one. Without any disks or even a hard drive, the BIOS program is always available, written permanently on the BIOS chip. It is used to set up the computer's hardware. Every time you boot your computer, you have the option of entering "Setup." Setup is how you access the BIOS program. Only experienced users should alter the BIOS settings. Improper BIOS settings can cause major problems on a computer. The BIOS chip contains enough information to operate the computer all by itself. When the computer is first turned on (or booted), the BIOS program is in charge. After booting and performing a few system checks, the BIOS program turns the computer over to your operating system. Windows XP is an example of a common operating system. CMOS, which stands for Complementary Metal Oxide Semiconductor, is where the BIOS stores its information. The CMOS area is usually located on the Chipset, or the Real Time Clock Chip (not the CPU clock). Some BIOS Chips also allow you to save your settings to EEPROM. EEPROM stands for Electrically Erasable Programmable Read Only Memory. Read Only Memory, (or ROM), is normally just that, and can never be erased or changed. ROM memory retains its data even when the power is disconnected. EEPROM memory also retains its data when the power is disconnected, but it can be altered by electrically erasing it, so that new data can be entered. If the CMOS looses its BIOS information, the EEPROM can provide your BIOS with a backup copy of the computer's settings. Below is a picture of a BIOS chip. This chip is where the BIOS program is stored.
