The document discusses operating systems and their functions. An operating system controls the entire operations of a computer by providing an environment for users to execute programs and acting as an interface between the user and hardware. It has two main objectives - managing hardware and providing an interface. The document then describes different types of operating systems including batch processing, multi-user, single-user, multi-tasking, real-time, multi-processing, and multi-threading operating systems. It concludes by listing some of the main functions of an operating system such as process management, memory management, file management, device management, security management, and providing a user interface.

1. OPERATING SYSTEM

2. OPERATING SYSTEM
• A set of system programs that
control the entire operations of the
computer.
• Provides an environment for the
user to execute programs.
• Acts as an interface between a user
of a computer and the computer
hardware.
• Has 2 objectives
– Managing the hardware
– Providing an interface
• Examples
– MS DOS, Windows XP, Windows 7,
LINUX, UNIX etc.

3. LAYERS OF COMPUTER SYSTEM

4. TYPES OF OS
• A Batch processing system
– A Executes only one job (batch) at a time.
– Collects similar jobs called batch and put them into a
queue.
– OS is responsible for scheduling the jobs according to
priority .

5. TYPES OF OS
• Multi user operating system
– Allows more than one user
can use the same data and
application programs at the
same time.
– Another term for multi-user
is time sharing.
– Eg: Linux, Unix, Windows
NT

6. TYPES OF OS
• Single user operating system
– Allows a single user to perform
only one task at a time.
– Eg: MS DOS.

7. TYPES OF OS
• Multi tasking operating system
– Allows multiple jobs to be executed
concurrently.
– Multiple jobs are executed by switching the
CPU between them.
– Eg: UNIX, Windows.

8. TYPES OF OS
• Real time operating system (RTOS)
• Designed to respond to an event within a
predefined time.

9. TYPES OF OS
• Multi processing operating system
– Can incorporate more than one processor
dedicated to running processes.
– Improves overall performance of the system.

10. TYPES OF OS
• Multi threading operating system
– A form of multi tasking.
– Allows multiple parts of a software
program to be run simultaneously.

11. FUNSTIONS OF OS
• Process management
• Memory management
• File management
• Device management
• Security management
• User interface