BIOS (basic input/output system) is the program a personal computer's microprocessor uses to get the computer system started after you turn it on. It also manages data flow between the computer's operating system and attached devices such as the hard disk , video adapter , keyboard , mouse , and printer .
BIOS is an integral part of your computer and comes with it when you bring it home. (In contrast, the operating system can either be pre-installed by the manufacturer or vendor or installed by the user.) BIOS is a program that is made accessible to the microprocessor on an erasable programmable read-only memory (EPROM) chip. When you turn on your computer, the microprocessor passes control to the BIOS program, which is always located at the same place on EPROM.
When BIOS boots up (starts up) your computer, it first determines whether all of the attachments are in place and operational and then it loads the operating system (or key parts of it) into your computer's random access memory (RAM) from your hard disk or diskette drive.
With BIOS, your operating system and its applications are freed from having to understand exact details (such as hardware addresses) about the attached input/output devices. When device details change, only the BIOS program needs to be changed. Sometimes this change can be made during your system setup. In any case, neither your operating system or any applications you use need to be changed.
Although BIOS is theoretically always the intermediary between the microprocessor and I/O device control information and data flow, in some cases, BIOS can arrange for data to flow directly to memory from devices (such as video cards) that require faster data flow to be effective.
CMOS complementary metal-oxide semiconductor) is the semiconductor technology used in the transistors that (are manufactured into most of today's computer microchips. Semiconductors are made of silicon and germanium, materials which "sort of" conduct electricity, but not enthusiastically. Areas of these materials that are "doped" by adding impurities become full-scale conductors of either extra electrons with a negative charge (N-type transistors) or of positive charge carriers (P-type transistors). In CMOS technology, both kinds of transistors are used in a complementary way to form a current gate that forms an effective means of electrical control. CMOS transistors use almost no power when not needed. As the current direction changes more rapidly, however, the transistors become hot. This characteristic tends to limit the speed at which microprocessors can operate.
Firmware is programming that's written to the read-only memory (ROM) of a computing device. Firmware, which is added at the time of manufacturing, is used to run user programs on the device.
When power is turned on, POST (Power-On Self-Test) is the diagnostic testing sequence that a computer's basic input/output system (or "starting program") runs to determine if the computer keyboard, random access memory, disk drives, and other hardware are working correctly.
If the necessary hardware is detected and found to be operating properly, the computer begins to boot. If the hardware is not detected or is found not to be operating properly, the BIOS issues an error message which may be text on the display screen and/or a series of coded beeps, depending on the nature of the problem. Since POST runs before the computer's video card is activated, it may not be possible to progress to the display screen. The pattern of beeps may be a variable numbers of short beeps or a mixture of long and short beeps, depending on what type of BIOS is installed.
The patterns of beeps contain messages about the nature of the problem detected. For example, if the keyboard is not detected, a particular pattern of beeps will inform you of that fact. An error found in the POST is usually fatal (that is, it causes current program to stop running) and will halt the boot process, since the hardware checked is absolutely essential for the computer's functions.
A beep code is the audio signal given out by a computer to announce the result of a short diagnostic testing sequence the computer performs when first powering up (called the Power-On-Self-Test or POST ). The POST is a small program contained in the computer's Basic Input/Output Operating System ( BIOS ) that checks to make sure necessary hardware is present and required memory is accessible. If everything tests out correctly, the computer will typically emit a single beep and continue the starting-up process. If something is wrong, the computer will display an error message on the monitor screen and announce the errors audibly with a series of beeps that vary in pitch, number and duration (this is especially useful when the error exists with the monitor or graphic components). The beeping sequence is really a coded message (beep code) designed to tell the user what is wrong with the computer.