Introduction to BIOS

 Basic Input / Output System (BIOS)

1.    boot the computer by providing a basic set of instructions

2.    load the operating system after turning on the computer

3.    perform POST (Power-On Self Test)

4.    provide set-up program for changing BIOS parameters

5.    provide low-level routines for the communications between OS and hardware devices

BIOS combination

1.    BIOS program

2.    CMOS stores BIOS program

3.    BIOS parameter

Advantages of storing BIOS in ROM

1.    code and data are readily available during booting
2.    BIOS content are not corrupted by errant applications

BIOS hardware components

1.    BIOS ROM

        a.    PC startup program (POST)

 2.    BIOS CMOS memory

        a   .    house the configuration information of individual PC

The BIOS ROM

1.    All BIOS are contained in ROM in old days

2.    BIOS is now located in EEPROM chip

        a.    erased and rewritten by special programs

        called flash BIOS

BIOS CMOS memory

1.    provide a non-volatile storage for PC’s control information

2.    need very little power to operate

3.    powered by lithium battery