Must See

1. OPERATING SYSTEM
A PPT BY AMOGH , ANKIT AND
MIHIR

2. Defination of operating system
The low-level software that supports a computer's basic functions, such as scheduling tasks and
controlling peripherals.
An operating system (OS) is system software that manages computer hardware and software resources
and provides common services for computer programs. All computer programs, excluding firmware,
require an operating system to function.
Time-sharing operating systems schedule tasks for efficient use of the system and may also include
accounting software for cost allocation of processor time, mass storage, printing, and other resources.
For hardware functions such as input and output and memory allocation, the operating system acts as an
intermediary between programs and the computer hardware,[1][2] although the application code is usually
executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by
it. Operating systems are found on many devices that contain a computer – from cellular phones and video
game consoles to web servers and supercomputers.
The dominant desktop operating system is Microsoft Windows with a market share of around 82%. OS
X by Apple Inc. is in second place (9.8%), and Linux is in third position (1.5%).[3] In
the mobile (smartphone and tablet combined) sector, according to third quarter 2016
data, Android by Google is dominant with 87.5 percent and a growth rate 10.3 percent per year, followed
by iOS by Apple with 12.1 percent and a per year decrease in market share of 5.2 percent, while other
operating systems amount to just 0.3 percent.[4] Linux is dominant in the server and supercomputing
sectors. Other specialized classes of operating systems, such as embedded and real-time systems, exist for
many applications.

3. Types of operating systems
Operating
system
Date first
released
Platform
MAC OS X
Apple
operating
system
history.
Apple
Macintosh
Mandrake
Linux
Unix and
Linux
history.
Various
MINIX
Unix and
Linux
history.
Various
MS-DOS 1.x
MS-DOS
history.
IBM
1.Simple Batch System
2.Multiprogramming Batch System
3.Multiprocessor System
4.Distributed Operating System
5.Realtime Operating System

5. Time-sharing operating systems
Time-sharing is a technique which enables many people, located at various terminals, to use
a particular computer system at the same time. Time-sharing or multitasking is a logical
extension of multiprogramming. Processor's time which is shared among multiple users
simultaneously is termed as time-sharing.
The main difference between Multiprogrammed Batch Systems and Time-Sharing Systems is
that in case of Multiprogrammed batch systems, the objective is to maximize processor use,
whereas in Time-Sharing Systems, the objective is to minimize response time.
Multiple jobs are executed by the CPU by switching between them, but the switches occur so
frequently. Thus, the user can receive an immediate response. For example, in a transaction
processing, the processor executes each user program in a short burst or quantum of
computation. That is, if n users are present, then each user can get a time quantum. When
the user submits the command, the response time is in few seconds at most.
The operating system uses CPU scheduling and multiprogramming to provide each user with
a small portion of a time. Computer systems that were designed primarily as batch systems
have been modified to time-sharing systems.

6. A real-time system is defined as a data processing system in which the time
interval required to process and respond to inputs is so small that it controls
the environment. The time taken by the system to respond to an input and
display of required updated information is termed as the response time. So
in this method, the response time is very less as compared to online
processing.
Real-time systems are used when there are rigid time requirements on the
operation of a processor or the flow of data and real-time systems can be
used as a control device in a dedicated application. A real-time operating
system must have well-defined, fixed time constraints, otherwise the system
will fail. For example, Scientific experiments, medical imaging systems,
industrial control systems, weapon systems, robots, air traffic control
systems, etc.
There are two types of real-time operating systems.
Real Time operating System