- BIOS - Basic Input Output System is a software that consists all the code required to control the disk drives, keyboard, mouse, display screen, serial ports and several other PC components.
- Act as a bridge between hardware & OS while booting. Like a nervous system in our body.
- BIOS monitors hardware changes (Hardware Independence)
- It is placed in motherboard’s EEPROM (Electrically Erasable Programmable Read Only Memory) chip.
- Cards like sound cards, Graphic cards has inbuilt BIOS chip called ROM BIOS chip.
Booting Process
- When the CPU is switched ON, BIOS starts working. First it shows chipset type, processor name, size of memory.
- After that, BIOS reads details in CMOS (Complementary Metal Oxide Semiconductor chip). CMOS is a RAM which is powered by small button battery to keep it ON when PC is OFF.
- Information about time, date, boot device etc. will be there in CMOS. This information can be changed by entering into the setup menu while booting.
- Next, BIOS checks the working condition of hardware. This is called POST (Power ON Self Test). BIOS boots the PC only when the POST gets passed.
- Then BIOS will start BIOS in all the cards like sound card, Graphic card etc..
- After checking the booting device using CMOS setting, it starts the OS in that boot device. If booting information is not available, error message appears.
- Even after OS is loaded, BIOS works continuously.
Flash update
If any new hardware is connected to the PC, sometimes PC will not recognize because Bios don’t know about it. BIOS can be updated through Flash update program.
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