M.Sc. IV Sem.
(Mathematics)
Paper 2nd - Fundamentals of Computer Science - II
Unit IV
Reference Book : C. Ritchie, Operating Systems incorporating UNIX and Windows,
BPB Publications, New Delhi.
Topic : Operating System (OS)
An operating system is a program which acts as an interface between the user
and the computer hardware. Every computer
must have at least one operating system to run
other programs. An application like Chrome,
MS Word, Games etc. needs some environment in
which it will run and perform its task. The OS
helps us to communicate with the computer
without knowing how to speak the computer's
language. It is not possible for the user to use any
computer or mobile device without having an
operating system.
Every general purpose computer must have an operating system to run other programs.
Operating system performs basic tasks such as recognizing input from the keyboard, sending
output to the display screen, keeping track of the files and directories on the disk, controlling
peripheral devices such as disk, drive and printers.
It is just like traffic cop. It makes sure that different programs and users running at the
same time do not interfere with each other.
The operating system is also responsible for security, ensuring that unauthorized users
do not access the system.
Examples : UNIX, MS-DOS, MS-Windows - 98/XP/Vista, Windows-NT/2000, OS/2,
Mac OS, Windows, Android, iOS, Linux etc.
Operating System Page 1 of 4 - Dr. Arihant Jain (98266-55655)
Function of an Operating System :
1. Process Management:- Process management helps OS to create and delete processes.
It also provides mechanisms for synchronization and communication among
processes.
2. Memory Management:- Memory management module performs the task of
allocation and de-allocation of memory space to programs in need of this resources.
3. File Management:- It manages all the file-related activities such as organization
storage, retrieval, naming, sharing, and protection of files.
4. Device Management: Device management keeps tracks of all devices. This module
also responsible for this task is known as the I/O controller. It also performs the task
of allocation and de-allocation of the devices.
5. I/O System Management: One of the main objects of any OS is to hide the
peculiarities of that hardware devices from the user.
6. Secondary-Storage Management: Systems have several levels of storage which
includes primary storage, secondary storage and cache storage. Instructions and data
must be stored in primary storage or cache so that a running program can reference it.
7. Security:- Security module protects the data and information of a computer system
against malware threat and authorized access.
8. Command Interpretation: This module is interpreting commands given by the end
acting system resources to process that commands.
9. Networking: A distributed system is a group of processors which do not share
memory, hardware devices, or a clock. The processors communicate with one another
through the network.
10. Job Accounting: Keeping track of time & resource used by various job and users.
Operating System Page 2 of 4 - Dr. Arihant Jain (98266-55655)
11. Communication Management: Coordination and assignment of compilers,
interpreters, and another software resource of the various users of the computer
systems.
Types of Operating system :
Batch Operating System
Multitasking/Time Sharing OS
Multiprocessing OS
Real Time OS
Distributed OS
Network OS
Mobile OS
Batch Operating System
Some computer processes are very lengthy and time-consuming. To speed the same process,
a job with a similar type of needs are batched together and run as a group.
The user of a batch operating system never directly interacts with the computer. In this type
of OS, every user prepares his or her job on an offline device like a punch card and submit it
to the computer operator.
Multi-Tasking/Time-sharing Operating systems
Time-sharing operating system enables people located at a different terminal (shell) to use a
single computer system at the same time. The processor time (CPU) which is shared among
multiple users is termed as time sharing.
Real time OS
A real-time operating system (RTOS) is an operating system (OS) intended to serve real-time
applications that process data as it comes in, typically without buffer delays. Examples:
Military Software Systems, Space Software Systems.
Operating System Page 3 of 4 - Dr. Arihant Jain (98266-55655)
Distributed Operating System
Distributed systems use many processors located in different machines to provide very fast
computation to its users.
Network Operating System
Network Operating System runs on a server. It provides the capability to serve to manage
data, user, groups, security, application, and other networking functions.
Mobile OS
Mobile operating systems are those OS which is especially that are designed to power
smartphones, tablets, and wearables devices.
Some most famous mobile operating systems are Android and iOS, but others include
BlackBerry, Web, and watchOS.
Operating System Page 4 of 4 - Dr. Arihant Jain (98266-55655)
