One beep from your computer at startup can make your whole day. Just ask anyone that has turned on PC and suffered agony of several beeps and then nothing.
When you purchase a computer, it will arrive with BIOS (Basic Input/Output System), pre-installed on an EPROM (Erasable Programmable read Only Memory), chip on main/motherboard. When you start your computer CPU (Central Processing Unit), sends control of PC to EPROM BIOS. The BIOS is part of POST (Power-On Self Test) of computer. Once BIOS receives go ahead from processor it starts its magical journey through all components and peripheral devices attached to computer. CMOS (complementary metal-oxide semiconductor), hold data that is accessed by BIOS setup. Basically, CMOS is reason that you can unplug your computer and retain startup and BIOS information. CMOS is maintained on motherboard in an always-on state supported by a battery installed on main board.
Much like human mind, when we wake up in morning our brain remembers that we have eyes, ears, a nose and so on. We know town we live in. You can go to work, stop by post office, grocery store and back home without having to spend time perusing a map for directions to each one. Your computer works much same way. Without a memory device to instruct computer on whatís where, operating system and other software would literally have to take time to locate each part of PC and its components every time they are loaded. Fortunately, BIOS take care of that for processor, operating system and components.
How BIOS works. Every computer comes pre-loaded with BIOS on motherboard. Motherboard manufacturers work long hours with BIOS manufacturers to make sure information in BIOS is specific to needs and components of motherboard. Although there are a number of BIOS manufacturers, two most popular are AMI (American Megatrends Incorp.) and VIA. BIOS simply put, is a program and not an actual device. It is software that informs computer at startup of all devices (input and output) attached to PC. The BIOS also lets you know when there is a problem. It accomplishes this by checking for known devices and makes sure they are still attached. When BIOS detect a problem it sends a series of beeps to motherboard speaker. This series informs user of what problem is, at least as well as BIOS can determine. Lets say your video card has gone way of XT model computer, BIOS senses that it has died or is not installed. The BIOS sends a series of beeps to onboard PC speaker to inform you of problem. Pretty neat! The problem is that no manufacturer of BIOS uses same beep series. This is why it is important for you to know BIOS software manufacturer for your specific PC. Weíll explain how to find this out later.
How do I know if BIOS are working? Thatís easy, if your computer starts and you get a single short beep, BIOS is working and has found and relayed information about input/output devices to CPU. If you turn on your computer and nothing happens at all, problem is probably in your power supply (this assumes that you have it plugged in properly) BIOS is probably still working but computer canít start because of a power problem. If all is well, BIOS will find all attached input/output devices, send a single short beep to internal speaker and computer will start boot process.