Introduction to the operating system
Even though the CPU is high-speed, it can do simple operations like adding to me
multiplying two numbers, etc., but not much more. Even simple activities like input or output of a name or converting a string of characters to uppercase or displaying an image on the screen must be built on top of these essential capabilities by writing a series of basic instructions
Also, the Computer has a large number of peripheral devices like keyboard, mouse, monitor, hard
disk, optical disk, printers, and other removable devices. Operating these devices require ting
long and complicated series of basic instructions
A modern computer system has a variety of resources like CPU, memory, secondary storage,
network, peripheral devices, etc. Multiple programs access these. Running concurrently
sometimes on behalf of different users with a different set of access rights. There needs to
be some "authority that regulates and mediates access to these resources.
A computer without any software for the above operations is a practically unusable device, because
it may not even have the primary user interface to interact with the user to provide a consistent
experience to the user, there needs to be a common framework for the standard mail. Computer
interactions. To strengthen the Computer, such a structure should also provide several types
of abstractions and metaphors. A file system metaphor is one such example that has discussed.
Thus an operating system exists to satisfy all these needs. Because it controls the whole system
it is always the first program to be started when the computer system is turned on.
What is an Operating System
An operating system is a controller, resource allocation standard services provider for a computer system. Like the government, it performs these functions to ensure smooth and mostly trouble-free
operation of the Computer.
The Startup Process of a Computer
When the Computer is supplied power and turned on the CPU takes control of the whole system
It initializes itself by bringing all its subcomponents in a known and ready-to-use state. Now it is like vehicle whose ignition has turned on and is ready to be driven" But where is the
driver" (the instructions to be executed by the CPU)? The Computer hs a type of permanent
memory called ROM (on personal computers, this is often called ROM BIOS (Basic Input Output
System or simply BIOS) that contains an initial program. This initial program, called POSLE(Power
On Self Test), performs a necessary check on all other components and peripheral devices in the Computer
and initializes them, so they are ready for us. Hence the next step in this sequence is to locate operating systems on the attached storage devices select the one to be loaded in many memories,
load it and start executing it. Once the operating system starts its execution, it takes control of
the entire computer system. This whole process is called "booting" the Computer to a particular
operating system.
Functions of an Operating System
An operating system (OS) performs a different set of essential functions as mentioned below
Providing hardware access as a basic service.
Controlling, Regulating and Supervising resources in the Computer
Handling Multiprocessor Systems
Starting and Stopping Program Execution
Controlling Access to the Memory
Serving Multiple Users at the Same Time
L Providing Security
Providing Other Common Services
Providing Hardware Access is a Common Service
In the earliest days of computing, each computer program would come with a set of instructions
To handle a fixed set of devices like printers, etc. If a new kind of printer added to a computer, it became necessary to add the instructions required to handle the new printer to every
Program to execute on that Computer. With the rapid increase in the number of devices and
device manufacturers as well as the number of applications to be run, this approach soon became
Infeasible. Thas, the operating systems started providing a simple service of handling the hardware
Devices. The code instructions) to control particular devices would be part of the operating system, and the operating system would provide access to these devices to individual programs as a standard
Service. When a new machine came into use, the original instructions needed to operate it would only
have to add to the operating system and thousands of individual programs spared of any the modification.
Controlling, Regulating and Supervising Resources in the Computer
Modem computers are far more potent than their humble predecessors and have access to at
Higher amounts of resources like processing power, main memory, storage, etc. As a result, they
Are now capable of running not just one program at a time, but many applications at a time. This ability is called multiprogramming. CreatesComputer a new message, as well. When only one program is
Running at a time, it has full access to all the resources, and there is my harm in it. But what
happens when many programs are running at a time and we programs start printing to the same
the printer at the same time or start writing to the same location of the same storage medium at the
the same time Obviously, access to shared resources must be controlled in such an environment
The operating system plays the crucial role of resource controller, regulator, and supervisor for
all hardware resources.
A computer system may have more than one CPU (processor) as well. A computer system
having more than one processor is known as a multiprocessor system. Operating systems for
ch multiprocessor systems are con
more complex than those designed only for single-processor systems. Managing which processor to use for execution is the job of the operating system.
Starting and Stopping Program Execution
When it begins initially, it runs only the operating system. The operating system takes
complete control of the computer system. It also runs a unique program called the shell. The shell
Duct a user interface (UD) to work. The user interface allows the user to indicate
What to do. It accepts requests for performing operations from the user (these requests
may be in the form of typing a command or clicking with a mouse, or touching on a touch panel, etc.) and initiates actions to fulfill those requests. If it is required to start a program to fulfill
requests, the operating system to do so. As the operating system has full control over
the network, only the operating system can start or stop programs.
Controlling Access to the Memory
The main memory is an essential resource for the computer system because it is the only large
scale form of mind that can match the speed of the CPU and can be directly accessed by the
CPU. Any program to be run must be loaded into main memory and any non-trivial data set to
Be manipulated must also be in main memory for the manipulation to occur. Hence this resource must be used judiciously. As a result, access to the main memory is also under complete
Control of the operating system, just like access to other resources. A process needing to get or
release some amount of main memory must request the operating system to do so and no means
Is permitted to access memory not allocated to it by the operating system. This is known as
memory protection
Serving Multiple Users at the Same Time
An operating system may be designed for use by only one user at a time (a single user system)
By several users simultaneously a multiuser system). With a multiuser operating system. It is actually
possible to run the programs of many users on a single computer usually called server, with each
the user performing input/output through their terminal that may have keyboard, mouse, and monitor
This is useful when all users cannot be provided with the powerful computers they need (due to
the cost factor) and a single powerful computer must be shared among many of them.
A multiuser system also provides additional benefits of centralized management and resource
(e.g., file) sharing. Sometimes, a computer system in a faraway corner of the world can be accessed
remotely by users over the Internet. This enables traveling employees of large organizations to access
their computers from anywhere in the world for doing their work. It also allows the technical support
of the organization to access computers in different offices and to diagnose and solve their
problems without wasting time on physical travel. Some companies even provide their employees with the option to work from their home.
Providing Security
When multiple users accessing in c in the same computer system, the operating system must provide a level of isolation between there so that one er cannot disturb the work of another user
At the time where there we collaboration joint project, they may be able to
Mme resources Hence the operating system must provide a security mechanism that ensures that
all authorized use of the support is permitted, while all attempts at unauthorized we are strictly
Denied. Modern operating systems are designed to provide such security.
With the heavy we of computer networks and the Internet, it is possible to be and
A computer system remotely possibly from thousands of kilometers away. While this facility
a boon for organizations having multiple offices around the world or for employees like a pro
and managers who have to travel a lot and still need to do their office computer, it can be
for gaining unauthorized access to mee's computer Modern operating systems provide
some base mechanisms to protect against such hazards, though they may not be sufficient by
themselves.
Providing Other Common Service
Apart from the functionalities, operating systems also offer my current services to make the operation of the computer systems tier. Many of these services remain hidden from the
because other programs on the Computer follow them and not by the human users directly
Operating systems also often come with some companion programs (utilities or accessories) that are small and simple and EFL to most of the Computer
These include a service to explore the information read on the Computer all browser, text editor, calculator program to view and edit images, a program to play audio and video, a web browser for sure the Internet. All operating systems, except for the embedded systems
be provided at least one shell program to allow the user to interact with the computer system
Though these do not entail part of an operating system, most operating systems come with some
such as a bonus. Some operating systems, especially the free ones, come with
a comprehensive set of software ready for daily use in different age scenarios like one
educational Institutes and office.
Typical Components of an Operating System
In this section, while discussing the components typically associated with an operating system and
the full environment surrounding the operating system. Keep visiting our 3.1 while reading the
description. This guide provides a simplified layered view of the operation or the computer system
in the context of operating system study
The Device Driver
At the lowest is the raw hardware of the Computer As we have seen earlier, this Parton
called the "raw iron," Is an immensely powerful system, but has no clue with as to what to do. This
layer also comes from various staff devices requiring potentially different to operate. The device drivers are small programs that contain the instructions
necessary for using these devices. While many of them come bundled with the operating system
SOe may have to be installed separately from a disk or the Internet. They are loaded and
unloaded as and when needed by the kernel. The kernel uses them for operating and controlling
the hardware.
The Kernel
The kernel is the core component or the main program of the operating system. A traditional kernel performs all the critical functions of an operating system including detecting new hardware when attached and loading appropriate device drivers to access it, accessing and controlling all equipment devices through the device drivers), resource allocation and management, creating, stopping and managing program execution, scheduling program execution, providing CPU, 1/O and memory Protection. I/O management, memory management, security, etc. By some definitions, the kernel IS the operating system.
