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(A) BIOS

The basic input/output system (BIOS) is also commonly known
as the System BIOS. The BIOS is boot firmware, a small program
that controls various electronic devices attached to the main
computer system. It is designed to be the first set of instructions
run by a computer when powered on. The initial function of the
BIOS is to initialize system devices such as the RAM, hard disk,
Fig. 1.19: BIOS Chip
CD/DVD drive, video display card and other hardware.
The BIOS sets the machine hardware into a known state to help the operating system to
configure the hardware components. This process is known as booting or booting up.
(B) Operating System (OS)
Learning Tip: An OS is a program which
An operating system is a program that acts as an
automatically gets loaded into the
interface between the user and hardware of computer’s main memory (RAM) at the
the computer as shown in Fig. 1.20. It helps to time a computer gets started. It provides
manage resources of the computer and optimize a platform to run other programs.
its performance. An OS is the first program to be
executed on a computer after the BIOS. It performs all basic tasks such as identifying basic
input/output devices, accepting input from the input devices, sending results to the output
devices, keeping track of files and directories on the disk, and controlling other peripheral
devices such as disk drives and printers.

System
Application Software
Software (Operating
System)

User
Computer Hardware
Fig. 1.20: Operating System as an Interface

 Need for an Operating System (OS): An
Application
operating system is considered as the most
important program of the computer. It
provides a software platform on the basis
Operating System Computer System (Additions)
of which other programs called application
programs run. It recognizes an input entered
by the user and controls various peripheral
Hardware
devices (such as printers/scanners) as shown
in Fig. 1.21. It also keeps track of the files and Monitor Keyboard
directories on the disk. The choice of selecting
Printer
OS depends to a great extent on the CPU
and other attached devices and applications Drives RAM
we want to run. For PCs, some of the most
popular operating systems are Microsoft
Fig. 1.21: Role of an Operating System
Windows, Linux, Mac OS, Solaris, BOSS, etc. 1.7