The operating system acts as an intermediary between the user and computer hardware. It provides an environment for users to execute programs and increases productivity of computer resources. The main functions of an operating system include process management, memory management, device management, information management, secondary storage management, and network management. It allows for the creation and deletion of processes and files, allocates memory and devices to processes, and maps files to secondary storage.

1. OPERATING SYSTEM
Operating system is a program that acts as an intermediary between a user
of a computer and the computer hardware.
Eg.DOS, LINUX, UNIX, Windows Operating System.
The purpose of operating system is to provide an environment in which a
user can execute programs.
Objective: To increase productivity of processing resources, such as computer
hardware or computer system-users.
 Goals of Operating System:
i) Convenience: Operating system is designed to provide convenience to the
user that is, the tasks can be computed easily in less time.
ii) Efficiency: It means making optimal use of computing resources for efficient
use of all the resources of computer system.
 Functions of operating system:
1) Process management functions
2) Memory management functions
3) Device management functions
4) Information management functions
5) Secondary storage management functions
6) Network management functions
7) Protection management functions
A.R

2. 8) Command interpretation functions
1) Process management functions: A Process can be thought of as a program
in execution. A process needs certain resources including CPU time, memory,
files and input output devices.
The major activities of an operating system in regard to process management
are
i) Creation and deletion of user and system processes
ii) Suspension and resumption of processes
iii) A mechanism for process synchronization and communication
2) Memory management functions: Main memory is a repository of quickly
accessible data shared by CPU and input output devices. The central processor
reads instruction from main memory during instruction fetch cycle.
The OS is responsible for the following activities in connection with memory
management.
i) Keep track of memory what parts are in the use and by whom? What parts are
not in use (free)?
ii) If multiprogramming, decide which process gets it and how much
3) Device management functions: One of the purposes of an operating system
is to hide the peculiarities of specific hardware devices from the user. For
eg.UNIX.
The peculiarities of input output devices are hidden from the bulk of the
operating system itself by the input output subsystem consist of:
i) Drivers for specific hardware devices. Only the device driver knows the
peculiarities the specific device to which it is assigned.
ii) Keep track of devices, channels and control units (I/O traffic controller).
iii) Allocate the resource (Device) and initiate I/O operation.
4) Information management function: A file is a collection of related
information defined by its creator. Commonly, files represent programs (both
A.R

3. source and object forms) and data. A file consists of a sequence of bits, bytes,
lines or records whose meanings are defined by their creators.
The operating system is responsible for the following activities in connection
with file management.
i) The creation and deletion of files
ii) The creation and deletion of directories
iii) The mapping of files onto secondary storage
iv) The backup of files on stable (non-volatile) storage media
v) Allocate the resource (information) i.e. open a file
vi) De-allocate a resource i.e., close a file
5) Secondary storage management function: Main memory is too small to
accommodate all data and programs, and its data is lost when power is lost, the
computer system must provide secondary storage to backup main memory.
The operating system is responsible for the following activities in connection
with disc management
i) Free space management
ii) Storage allocation
iii) Disc scheduling
6) Network management functions: The processors in the system are
connected through a communication network, which can be configured in a
number of different ways. The network may be fully or partially connected .The
communication network design must consider routing and connection strategies
and the problems of contention and securities usually generalise network access
as a form of file access, with the details of networking being contained in the
network interface device driver.
A.R

4. WINDOWS OPERATING SYSTEM
Microsoft’s windows family consists of various graphical user interface
(GUI) based operating systems. Since GUI based interfaces are more user
friendly compared to CUI based interfaces. The most popular windows
operating systems in use are Windows 95, Windows98, Windows NT,
Windows2000 etc.
 Features of Windows:
i) True 32-bit operating system: A computer stores and processes data in bits,
the efficiency of an operating system depends on the number of bits it can
process at a time. Windows 32-bit operating system can send, receive and
process 32-bit of information at a time.
ii) Portability: The ability of an operating system to run on different
microprocessors is referred to as portability. Windows is one such portable
operating system, which can run on different microprocessors like INTEL
80486, PENTIUM etc.
iii) Scalability: Windows can use multiple microprocessors for processing data.
In fact, a Windows server can support as many as 32 microprocessors
simultaneously.
iv) Multi-tasking features: Windows is a multi-tasking operating system,
which means that it can simultaneously perform more than one task. Multi
tasking is implemented using the principle of time sharing, where each task is
allowed to run only for a fixed duration of time.
v) Multiple user support: Windows is a multi user operating system, which
means that it supports many users at a time. Several users can access the same
files and share the same resources stored on the computer.
vi) Compatibility: Windows is compatible with other operating systems for
networking and sharing resources.
A.R

5. vii) Graphical user interface: Windows has a user friendly graphical interface.
Users can perform complex tasks by selecting options from drop down menus
and clicking icons to execute programs.
viii) Extensibility: The extensibility of windows provides the flexibility of
adding computers to the network.
ix) Customisable interface: Windows can be customised to suit user specific
requirements. You can change desktop colours, fonts and modify system
configuration to suit your requirements.
x) Built in networking: Windows supports networking by using client/server
architecture. Each computer can communicate and access resources and data on
the server as well as on other computer.
A.R