University of Tabuk College of Computer and Information Technology CSC 410: Oper

Question

University of Tabuk College of Computer and Information Technology CSC 410: Operating Systems Summer Semester 2017-20181 1437-1438 Title: Homework #1 (covers chapter 1). Due Data: Thursday, 12/7/2018 (submitted it in the class time)- Question 1 What is an operating system? What are the mais purposes of any operating system Question 2 Computer system can be divided into components What are they? Explain each one of them in your own words Question 3 Explain what we mean by caching principle. Question 4 The operating system is responsible for five activities in connection with process management. What are those activities? Question 5 In your own words Explain the following terminologies in the point view of operating systems: Protection in operating systems Security in operating systems Virtualization in operating system Open-source operating system

Explanation / Answer

1)

Operating System:-

An operating system acts like an interface between the system hardware and the user applications. It is one the most important software of the computer that is responsible for managing the software and harware resources. This usually gets loaded at the boot time and helps us to communicate with the system hardware and software without us knowing the computer language.

Purposes of Operating System:-

1) Provides an interface between the application of user and hardware

2) The Operating system is responsible for the allocationo of memory resources.

The main purpose of the operating system is to allow the user carry out his work without being bothered about trivial tasks such as managing memory, flushing the cache, initializing the hardware etc. In short, it manages all the hardware related activities.

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2)

The Componenets of Computer :-

a) Input Unit

This unit deals with all the input devices of the computer. An user uses these devices to interact with the computer. Eg:- Keyboard, Mouse.

b) Output Unit

This unit is responsible to display the data that the computer has computed to the user. It connects the computer to the external world. Eg:- Monitor, Speakers etc.

c) Processing Unit:-

This unit is called the brain of the computer. This is where all the computation of the data takes place. This device is also responsible for giving the memeory resources to various programs.

This unit consists of three units Memory Unit, ALU, Control Unit.

It stores data, intermediate results, and instructions (program). This unit controls the operation of all parts of the computer.

d) Storage Unit

This unit is part of the central processing unit.

Responsible for storing the data and instruction so that they are available to the processor as and when required. The user enters data, this data has to be stored somewhere before it actually gets processed, The data gets stored in the storage unit.

This unit consists of Internal Memory devices(RAM,ROM,HARD DISK).

e) Arithmetic Logic Unit

This is a part of the CPU.

This unit is responsible for all the arithmetic operation such as addition,subtraction,division etc. All it does it takes the information from the memory devices crunches the number and passes out the output.

It likes the calculator of the computer. It doesnt care about the status of the data. All it does is computations.

f) Control Unit

This unit as the name suggests controls the flow of data. This decides which components the data should be taken from and where should it be passed. This device is also repsonsible for sending the input to ALU and also diverting the output to the required device.

Control Unit maintains the order and directs the operation of the entire device.

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3)

Caching Principle :-

Before we go into Caching principle let's just recap how a computer works.

A CPU accesses data from the memory unit and computes the data from the memory and send the data back to the desired device.

All This looks simple right, But it is not. We generally tend to think that whenever a CPU requires data from the memory device it gets the data immediately. But That's not always the cahce. Suppose we have a single bus computer then in that cases, when a CPU is working on one specific instruction the bus is busy and the CPU need to wait until the bus is empty.

So you see there is a time lag.

Basically what i mean to say is that, A CPU might have to wait to get the data due to different operating speeds of the devices. In such cases the waiting time of the program increases and it's just a waste of time.

So in order to overcome it, People built something called as Caches.

These Caches are small memory devices which are fit into the processor itself. So in this way The Cpu does not have to wait for the data to travel from RAM to CPU. It can use the cache.

The Caching principle tells all about the memory hierarchy. The program needed by the CPU is first loaded into the RAM from the memory devices and as we know each program is maded of many instructions. So the data needed for a instruction is loaded up into the cache. So in this way, When the CPU is executing one instruction, the next instruction can be loaded up into the cache for the immediate use of the CPU.

Remember the farther the Memory device is from the CPU, The slower the access time.

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4)

The Five activities of Operating System:-

a) Creation and Deletion

The Operating System is responsible for the creation and deletion of the process. Suppose you start an application A OS is responsible for handing out memory resources to it and and realeasing the memory resources for other applications when you exit the application.

b) Suspending and Resuming

Some times, when there are many processes working open at the same time. An OS is responsible to check the processes which are not in use and suspend thoose so that other processes can acces that memory. And when a user click on the suspended process it is also responsible to resume it.

c) Synchronising

An operating system provides a way for two processes to work at the same time. Just like using a web browser and playing songs at the same time.

d) Communicating

An operating system helps facilitate the communication between two processes. For eg:- You Python application might need to talk with your web browser. An OS is responsible for that.

e) Dead Lock handling

When a number of running processes are all in a paused state, each one waiting for resources currently being used by another running process, deadlock can occur. This could cause all programs to halt indefinitely if the operating system did not intervene. The operating system can take steps both to avoid and end deadlock should it happen.

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