Introduction to Computer Operating System

 

Introduction to Operating 

System Concept

OPERATING SYSTEM CONCEPTS

·                             What Operating System Do
·           Computer-system Organization
·           Operating-System Operation
·           Definitions    

What is an operating system?

operating systems every day and you can look at this little figure over here and see that an operating system is software that is goes in between the applications that run on a computer and the hardware

an operating system is software that goes in between the applications that run on a computer and the hardware.                              

A program that acts as an intermediary between the use of computer and the computer hardware

 Operating system goals:                         

§           Execute user programs

      Make solving user problems easier

§          Make the computer system convenient to use

§         Use the computer hardware and resources in an efficient manner

 well, the goal of an operating system really doesn't do anything   on  its own other the way than maybe some maintenance but its goal is   to execute the applications on the system the user programs to make   solving problems easier to make your computer system convenient    to use and to use the hardware and the resources in an efficient way

what do the operating systems do?

the operating system just hides how everything's being done and makes everything work very smoothly from the system point of view the operating system allocates the resources so lets out water resources.

 here are some definitions resource process deadlock buffer and cash a resource is a component in a compute in it's a component in anything but for our purposes and operating systems it's a component of limited availability that is necessary for effective operation

so, a resource is whatever any process needs to use to complete its tasks memory CPU files data anything that's needed to complete tasks a process you might think is a program in execution.

OS is a manager that needs to use all the resources to perform management duties

Definitions

·       Resource

   Component of limited availability necessary for the effective    operation

·       Process ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­-

Active program

·       Deadlock-

    A situation in which tow or more competing actions are each      waiting for the other to finish, and thus neither ever does.

·       Buffer-

   Area of memory that stores data

·       Cache-

   Area of fast memory that store's couple of data

so, a resource is whatever any process needs to use to complete its tasks memory CPU files data anything that's needed to complete tasks a process you might think is a program in execution

 but as you'll find as we go through the lessons in this course you will find that if you only have one CPU then only one process can actually be executing at a time so a process is actually an active program and what do you think a deadlock is well a deadlock is a situation in which two or more processes are waiting for each other and none of them are moving forward because they're all stuck waiting for each other and

so, a buffer can store any kind of information between two processes or between a process and a device but a buffer is just an area of memory where data is stored.

 and this data maybe the only copy of that data and a buffer is usually volatile storage which means that it that copy of that data could be lost if the computer is turned off the cache is an area of very fast memory that is associated with your processor that stores copies of data so a lot of times things get cached and they put in the cache for faster reference.

but then you have cache coherency problems because you want to make sure that you're always working with the most up-to-date information

so, what is the difference between a buffer and a cache they both store data but a buffer has the only copy of the data and a cache there might be another copy somewhere else and a cache is also designed to be much faster than just a buffer.

 that storing information so a couple more definitions the kernel of the operating the system is the one process that is not actually running all the time but is of all the time.

 so when your computer system get started the coat with a kernel the core of the operating system also gets started and gets ready and some operating systems depending on how the operating system has been structure structured the kernel may be very small or it may be very large because the operating system is dedicated to doing a lot of things and this is some of the information.

 so, everything else that's that runs on your system is either comes with the operating system as a process or an extra program or is an application program.

 and interrupts let's talk a little bit about interrupts and interrupts is just a change inflow of execution so if a process is executing and it has to stop and interrupts happens and the operating system needs to deal with interrupts because it may be interrupted in the middle of doing something and there have to be handlers that handle all these interrupts most modern.

 operating systems are interrupt-driven what that means is most operating systems like on your the personal computer they wait for someone to type in a command or click a mouse or start something in order to handle what they're going to do so most of the time everything happens in operating systems happens because of an intro not be not everything but most activities.

 some of the activities happen while the operating system is checking for things but most of the time it just sits there waiting and then it handles interrupts and you should be familiar with the different types of storage there's a volatile storage which you lose if the computer turns off and there's persistent or non-volatile storage which is maintained like on your hard disk or you’re anything that is it you don't lose when the computer is turned off

so, this is just a little overview of how a computer system is organized and you have your CPUs and everything is competing for every whatever you want to do needs to be put into memory and then it is moved and instructions are handled by your CPU.

so, you have all of your devices and your CPU that are executing concurrently and you have controllers for your devices which are the some of your devices come with their own controllers and the devices have their own local buffers and your PCP you will move data to and from the main memory and to and from the buffers and

your input and output is from a device to a local buffer of you're of a controller and everything happens and causes interrupts and the operating system deals with these interrupts and has to manage all of these resources.

 and all these resources for all of these products so again like I said it's interrupt-driven so what happens when an interrupt the control goes to an interrupt service routine and then the important part about it is that when an interrupt happens the operating system needs to save the current instruction

 so, when it loads again it will load where it was interrupted and not have to restart at the beginning but in order to do that the operating system has to use the resources and that's called overhead

so when an operating system is performing its management tasks and using the resource the resources that are called overhead so we did a little introduction into some definitions and read the notes and thank you very much.