The document discusses the role and definition of operating systems. It describes how a computer system can be divided into four main components: hardware, operating system, application programs, and users. The operating system controls and coordinates the hardware resources among applications and users. It acts as an intermediary between the computer hardware and users to make the computer system more efficient and easier to use. Operating systems come in many varieties depending on the type of computer and its intended use.

1. Operating System Concepts
Prof Neeraj Bhargava
Vaibhav Khanna
Department of Computer Science
School of Engineering and Systems Sciences
Maharishi Dayanand Saraswati University Ajmer

2. Computer System Structure
• Computer system can be divided into four
components:
– Hardware – provides basic computing resources
• CPU, memory, I/O devices
– Operating system
• Controls and coordinates use of hardware among various
applications and users
– Application programs – define the ways in which the
system resources are used to solve the computing
problems of the users
• Word processors, compilers, web browsers, database
systems, video games
– Users
• People, machines, other computers

3. Abstract View of Components of Computer

4. What Operating Systems Do
• Depends on the point of view
• Users want convenience, ease of use and good performance
– Don’t care about resource utilization
• But shared computer such as mainframe or minicomputer must keep
all users happy
– Operating system is a resource allocator and control program making
efficient use of HW and managing execution of user programs
• Users of dedicate systems such as workstations have dedicated
resources but frequently use shared resources from servers
• Mobile devices like smartphones and tables are resource poor,
optimized for usability and battery life
– Mobile user interfaces such as touch screens, voice recognition
• Some computers have little or no user interface, such as embedded
computers in devices and automobiles
– Run primarily without user intervention

5. Defining Operating Systems
• Term OS covers many roles
– Because of myriad designs and uses of
OSes
– Present in toasters through ships,
spacecraft, game machines, TVs and
industrial control systems
– Born when fixed use computers for
military became more general purpose
and needed resource management and
program control

6. Operating System Definition (Cont.)
• No universally accepted definition
• “Everything a vendor ships when you order an operating
system” is a good approximation
– But varies wildly
• “The one program running at all times on the computer” is
the kernel, part of the operating system
• Everything else is either
– a system program (ships with the operating system, but not
part of the kernel) , or
– an application program, all programs not associated with the
operating system
• Today’s OSes for general purpose and mobile computing also
include middleware – a set of software frameworks that
provide addition services to application developers such as
databases, multimedia, graphics

7. OS as an Extended Machine
• An operating system is the most important program in a computer
system. This is one program that runs all the time, as long as the
computer is operational and exits only when the computer is shut
down.
• The fundamental goal of computer systems is to execute user
programs and to make solving user problems easier. Hardware of a
computer is equipped with extremely capable resources – memory,
CPU, I/O devices etc.
• All these hardware units interact with each other in a well-defined
manner. Also various programs require certain common operations,
such as those controlling the I/O devices.
• The common functions of controlling and allocating resources are
then brought together into one piece of software: the operating
system.

8. • Operating systems exist because they are
supposed to make it easier to compute with them
than without them.
• Efficient operation of the computer system is a
secondary goal of an operating system. This goal
is particularly important for large, shared multi-
user systems.
• Operating systems are the programs that make
computers operational, hence the name
Operating (the )system.

9. Operating System as an Extended
Machine