Ever wonder what goes on in the background or within the computer's system or
motherboard once you press the power button on? Which program runs or software
runs first? Let this article take you through the process.
Once your computer is turned on, its microprocessor found on a single micro
chip which functions as its central processing unit (CPU) awaits for its first
command. The instruction cannot come from the Operating system since it is
stored on a hard disk and the microprocessor would need to be directed to it.
This is where the function of the Basic Input/output System or BIOS, pronounced
as "bye-ose" comes into play. It is a system soft ware that ensures
all programs, chips, hard drives, ports and even hardware are working properly
as it powers up your computer and let you start working.
It simply allows the microprocessor to communicate with the Operating System
and its applications and then detects all hardware (mouse, keyboard) installed
or attached to get your computer all ready to start.
Here are
the steps that BIOS follows to fire up your computer:
- confirm your CMOS set up for your computer's settings
- Initiate interrupt handlers/device drivers
- Enable system registers and power operation
- Conducts power-on self-test (POST)
- Presents the system's settings
- Decides on which devices are bootable
- Begins bootstrap sequence
BIOS primarily checks information kept on a tiny 64 byte (RAM) chip found on a
complementary metal oxide semiconductor (CMOS). It displays pertinent
information particular to your system's default settings which can be modified
by the user or as deemed necessary by BIOS.
A typical PC will show you a CMOS set-up dependent on their BIOS manufacturer
with several options such as: System Time/Date; Boot Sequence; Plug and
Play; Mouse/Keyboard; Drive Configuration; Memory; Security; Power Management
and Exit. Hitting a key or combinations like "Esc,"
"Del," "F1," "F2," "Ctrl-Esc" or
"Ctrl-Alt-Esc" will allow you to go into the CMOS set-up screen.
Although, you can alter your computer's custom settings take extra precaution
in doing so to avoid any system issue that may arise.
Acting as an interpreter between the operating system and its components or
hardware are the Interrupt handlers. To cite an example, this type of software
enables the CPU to know which key you pressed on the keyboard via signals and
passes it to the Operating System. While, device drivers detect components
attached to your computer such as keyboard, hard drive, floppy
drive and mouse.
BIOS may also perform a power-on self-test (POST) to confirm that all hard ware
or components are functioning. It will then eventually try to launch the
Operating System as determined by the boot sequence - the order in which BIOS
will begin loading the Operating System.
It's amazing to note that a simple process such as turning on your computer
requires a series of steps to make it work. It'll start from the microprocessor
receiving its first command to initiating the sequence of booting the operating
system to powering all computer hardware or components which are made possible
by this one essential software known as, BIOS.
