The document discusses the functions and objectives of an operating system (OS). It notes that an OS acts as an interface between the user and computer hardware, managing devices and providing a simpler interface to programs. The key objectives of an OS are convenience, efficiency, and the ability to evolve over time. The functions of an OS include program development, execution and scheduling, providing access to I/O devices, controlling access to files, system access control, error detection and response, and accounting. The OS also acts as a resource manager, allocating memory and resources efficiently among processes.

1. B.Abinaya bharathi
I-M.Sc[Cs&IT]
Nadar Saraswathi college of Arts and Science,
Theni

2. * An operating system is a program that acts as an
interface between the user and the computer hardware and
controls the execution of all kinds of programs.
* OS is a layer of software whose job is to manage all
devices and provide user programs with a simpler interface to
the hardware.

3. Objectives of OS
* Convenience
* Efficiency
* Ability to evolve
Convenience: OS makes a computer more convenient to use.
Efficiency: OS allows the computer system resources to be used
in an efficient manner.
Ability to evolve: OS should be constructed in such a way as to
permit the effective development, testing, and introduction of
new system functions without interfering with service.

4. Functions of OS
* Program development
* Program execution
* Access to I/O devices
* System access
* Controlled access to files
* Error detection and response
* Accounting

5. Functions of OS

6. Program development
* OS provides a variety of facilities and services, such as
editors and debuggers, to assist the programmer in creating
programs
Program execution
* To execute a program first we need to load the data,
* Needed devices are initialized .OS handle all these
scheduling duties.
Access to I/O devices
* Each I/O devices use some set of instruction for
operation ,OS provide a uniform interface that provides the
user to acess the I/O device.

7. Controlled access to files
* OS must reflect a detailed understanding of structure
of the data contained in the files on the storage medium
. * OS provide a protection mechanisms to control access
to the files.
System access
* In a public system ,the OS control the access to a
system.
* OS protect the data and resource from unauthorized
users.
Error detection and response
* Error may occur while system running like device
failure , software error, etc,.
* OS must clears that error condition.

8. OS as a user /computer interface
* user view of the computer refers to the interface being
used
* The goal of the Operating System is to maximize the
work and minimize the effort of the user.
* Most of the systems are designed to be operated by
single user, however in some systems multiple users can share
resources, memory.
* In these cases Operating System is designed to handle
available resources among multiple users and CPU efficiently.
* Operating System must be designed by taking both
usability and efficient resource utilization into view.

9. OS as a user /computer interface

10. OS as a Resource manager
* Operating System is allocator, which allocate
memory, resources among various processes.It controls the
sharing of resources among programs.
* It prevents improper usage, error and handle
deadlock conditions.
* It is a program that runs all the time in the system in
the form of Kernel.
* It controls application programs that are not part of
Kernel.
* It mamages the resources efficiently.

11. OS as a Resource manager

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