Bios and Post

1. BIOS (basic input/output system)
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.
Difference between Bios and Cmos- The main difference between
BIOS and CMOS is that the BIOS is a firmware that performs hardware
initialization when booting up the computer and provides runtime
services for OS and other programs while the CMOS is a special
memory chip that stores and retains the BIOS configuration settings.

2. POST - POST stands for "Power On Self Test." It is a diagnostic
program built into the computer's hardware and Run my Bios that tests
different hardware components before the computer boots up.
The POST process is run on both Windows and Macintosh computers.
While the exact tests performed may vary between machines, most POST
sequences check the vital hardware components, such as the power
supply, RAM, and system bus. If any of these tests fail, the POST process
will return an error message. This message may be displayed on the
screen or may be output in the form of beeps or blinking lights.
The most common type of POST error is a memory error. This can be
caused by one or more bad memory modules or a memory chip that is
loose or not fully seated. If the post process fails on your computer, you
may need to check your computer's manual to see what the error code
means. If it is a memory error, you may be able to fix the problem by
removing, reinstalling, or replacing the bad memory module. If the error is
caused by another component, you may need to have your computer
serviced by an authorized technician.
The POST process runs quickly at the beginning of the boot
sequence before the operating system loads. Therefore, you most likely
will not notice it unless there is an error. If the POST process finishes
without encountering any errors, your computer will boot up normally.