What is the sequence of things done by the BIOS when you turn on your Computer?
When the computer is first turned on, the BIOS instructions are initiated. The BIOS will then conduct the following tasks in order:
- Enumerates the RAM by checking each compartment to see that they are all working
- Then checks for other devices attached to the computer
- Detects all the peripherals, including the keyboard and mouse and then checks for the boot options
- Checks boot options in the sequence configured on the BIOS. Eg. Boot from CD-ROM, Boot From Hard Drive, Boot from LAN etc.
- Checks for bootstraps on the devices as configured on the BIOS
- Loads the essential parts of the OS into the RAM, and hands over control
There are a lot of other things that a BIOS does, such as check the CMOS and other chips, and load device drivers into the memory, among other things. However, these are the primary function of the BIOS.