So what operating system basically is...


Operating system is a system software means it's a software which is in your system

And its basic functionality or definition is...


It works as a interface between user and hardware.
It's in very simple language that operating system
is providing interaction between user and hardware.


Now if we'll see in this diagram first which of these is hardware .If we'll take scenario of our laptop.In our laptop or desktop


What hardware basically is CPU

Which we call brain of the system.
CPU... Then input, output devices which includes keyboard, mouse, printer, scanner then RAM that we call the main memory then secondary memory i.e. Hard Disk.


So when we access a lot of these hardware.When i'm accessing my system,then I'm just accessing these devices.


But... Am I directly accessing those devices?

Is the user directly accessing
the hardware and devices?....

NO




He's accessing through what?....

Through operating system,

Operating system is working as an interface here then second point is

Why there's a need of operating system ?
If there'll be no operating system
then what will be the scenario.
So the scenario will be that if user wants to access
a particular hardware, he have to write a program for it

And through that program
he'll always access that device
Means he always have to write
a program to access those devices.

He have to write different programs for different devices again and again.

So when he'll write this much program in repetition.

I have to give a print command simply
I have a word file that needs to be printed then I can't print it directly.


First I have to write a program for it.

So that printer will
know it that it has To print
1.Similarly if we'll talk about CPU.
If I want to execute a process or a job then that job execution is later work, first we have to give CPU an instruction,

And how we'll give that instruction?
For that we have to write individual program

And because of that the interaction between
user and hardware will be very complex.

There could be another way also...
It could be possible that user is accessing one hardware

And if other user wants to access that hardware
then I'm not releasing it... Why?

Because I'm the user accessing
the hardware directly, means there's no authority in between
who can take back the hardware from me.


So there're a lot of reasons because of
which we need to use operating system.
That's being used as an interface
 between user and Hardware
We'll see that in functions,
All the functions of operating system,
we can call them as these are the reasons
 why we are using operating system in our system.



So if I'll give basic example of operating system. So the first operating system that's used in majority is Window's.

Now primary functionality of operating system.If we'll say why we are using operating system

The major\primary goal of operating system is To provide convenience...

To provide convenience to the user

Yess...
It provides convenience means I can access my hardware in easiest way

That is the functionality of operating system
And this is the reason that's why Window's acquired the whole market up to many years.There was a time when Window’s
acquired 95% of the market means the whole market was acquired
 by Microsoft...

They had this much popularity!
Because the major goal is convenience, and window's is providing convenience the most

If you'll see in your or your friend's laptops,
the operating system you'll get is window

There could be different versions in Window's
like 2007, 2008 etc that depends.But why are we providing Window's basically?


Because of convenience, but gradually with time, the problems that we were solving
in our systems started to get complex

And the value of time is increasing so much for the user Means user wants, that his problem should get execute very fast and for that we need through put

What through put means in a simple definition is
Number of tasks executed put unit time.That is a simple definition of through put.So the more no. of tasks are getting executed in a particular amount of time, the more will be my through put.

 It means we need such operating systems now whose
through put is high as well as convenience is high.
So the maximum use in through put is Linux
Although Linux operating system doesn’t mean
that it's not providing convenience

I'm just comparing it because why window's acquired 95%
of the market because of the only reason i.e. convenience.
But now if we'll see at present in 2018,
it is approximate 82%

Means, now their acquisition in market
has become low as compared to last years.
Now Linux, that was in 1-2% before
 has now increased because of through put
And other than this we are having
Apple's it's own operating system that is Mac or Macintosh, that also
runs well in the market.
But that is a different thing...
these are
 real life example like window's, Linux and Macintosh

But the major goal is
convenience and through put
Next part that comes here is

What are the functionalities of operating system ?


Means if I've put operating system in
my system, then what are its functionalities
Then major functionality of operating system is
First one is, resource governor or resource manager

It manages the resources
How we manage resources?

If I'm an alone user and accessing my system by my own
Then at that point I don't need
resource governor that much
Means, where ever there is parallel axis
Means when multiple user are accessing a system that works happen in majority on server level.
If we would talk about a server where a lot of users
are sending requests to access some data at that point operating system is useful
and works as resource manager


How much hardware to be provided to which user
or for how much amount.
That is done by the operating system
after that time it will take back that device from the user.


This is how we manage resources
so that there'll be no load on the system the moment we open normal task manager
 in our system

.

Then you'll easily get a lot of values like that how much percent we are using CPU, How much the RAM
All that values are managed by operating system.

So there'll be no that much load on the system
and not much less also means it tries to manage resources properly.
But specially where it uses is parallel processing,
where multiple users are trying to access one device.


Second point is storage management Or we can say it as process management
process management means we are managing processes in majority in our system
 
Means we are executing processes, I opened
the laptop and I'm working on Microsoft word on it
Along with that I've opened my Window Media player also Along with that I've opened gaming app also
Means I'm sitting with multiple process opened.



How to execute all these processes...
that is also done by the operating system
.
How it works??...
CPU scheduling
 Here we use CPU scheduling algorithms CPU scheduling means... If I wrote
a simple program and saved it with .C, now I want to execute that program then that program became process.
Now if we want to execute the process
then where will we do it?... at the CPU.
Now how to execute that process at CPU...
That is done by the CPU scheduling
And there comes a variety of algorithms that
are useful to access and execute in a efficient way.
And who is handling
 all that management?...

Operating system


 
Other than this we have storage management
Storage management means... Basically storage includes secondary devices i.e. Hard disk Means the data that we want
to store in our system permanently.

Operating system is managing how to store that data And how we do storage management?...

Through file system
NIFS, CFS etc... CIFS and NFS
Common interface file system, common internet file system and networked file system
all these get used in Linux and Window's their major goal is...

It manages how to store all my data in the hard disk permanently. That how to store it in tracks or sector in disk's architecture, that is also managed by the operating system.

Then fourth one is memory management.
In memory management,
what I have here is RAM.Because...
If we would say why we have separated
storage management and memory management, because storage management consist hard disk, It's operating system's functionality to manage
hardisk but there's no constraint of hard disk, we have a constraint in RAM i.e. limitation of size Means RAM in our system is limited.


And all the processes gets
executed first in the RAM.
This topics is called the concept of multi-tasking or multi programming means all the processes that we have to execute.


We bring all that first of all in the RAM
And when it comes in the RAM, then we transfer it to CPU one by one.

So how much memory of the RAM we have to give
and take that memory back when the process is done

 
Allocation & Deallocation

Because the RAM is limited.
It shouldn't be like, the process has
become executed but it's still in the RAM.
And the other process that wants to get executed
is not able to come in RAM, because it's full already so what operating system does is... When a process is done,
then it takes out of it and bring the other one.


This is called the swapping,
so these are
whole individual topics and units, it's just I'm discussing here that what the functionalities are I've already discussed about them, I have created whole videos on it.
Where we've talked about memory management, Storage management and disk or file system, we have already discussed CPU scheduling
and resource management.


Other than this we have 5th...
I'm writing the functionality here i.e. security.

Security and privacy...

It's also provided by the operating system.
Whenever we turn on our system, what we first get is the password.


So why we put that password?....
So that authenticate person who have
 its proper password can access it
And window's uses Kerberos security protocol to keep that password properly in secured files so that no one can access it.


Other than this, in the RAM as I told before,when we executes a process then it gets a portion in the RAM, like it got a memory allocation 0-100

One process is P2 , it got
memory allocation of 101-200.

If any process calls or executes any instruction outside the given segment, then that process gets block instantly.
Means if any instruction of P2 is accessing the data or interfering in the data, then that process gets blocked.
Means it's providing security in between the processes so that no processes can do interfere
or data change with each other.
So security and privacy is also provided by the operating system.I've many other functionalities here but these are major functionalities of operating system.Here I would like to tell a last point here,

that as I wrote in diagram, user application.



What's the application here is....


How do we access operating system
as a normal user.
If you'll notice when you turn on your laptop
 then desktop appears, that's an interface,
we can go to my computer, can access data,
We can access any movie or song in C, D, OR E drive.
Now in actual, user can either access through application or can access direct also.


We uses application in majority, like if I want to print a particular file then what I do is,

First I'll create that file in Microsoft office.
That a kind of application...
when we enter ctrl+ P,
then it asks
"Do you want to print'... Yes?
then you gave the print command.


What is that print command actually?
We are accessing the hardware with it.
But you are accessing the hardware through the application directly, and operating system is working as an interface here.

Do you feel anything like that?...

No


We as a user don't feel this.So it's providing so nice interface that user don't even feel when
they're accessing the hard ware and when not
Or the other way is shell Like if we would talk about window's then we can access the operating system
or kernel through command prompt.


And in Linux, we opens the terminal
and can write the command directly in it.That's through the command prompt... we have to
write particular command in it that's called...

System call.



Operating system basically works in system call,whenever
operating system will work...
It'll work through system call.
So whenever we are giving a command through application like print,then print will invoke a system call
and that system call is right.
Sameway if you are opening a file
in C or D drive with double click


We just opened normally with
double click and file got open.

But how operating system opened that file??through open system call.


Means there're a lot of system calls like read, open, right
 
through which operating system works
between application, user and hardware.

So these are basic functionalities or goal of
operating system that you have to keep in mind
.
It can be asked in normal theory, or GATE or UGC NET
.
In majority it will come in your
 college or university level exams
.


Thank You!