Exam Answers: Operating Systems, Job Scheduling, And Process Interaction Essay.

Besides the usual Windows/DOS/Windows Phone, MacOS/macOS/Classic MacOS/Apple IOS and Linux/Unix/Android Operating Systems, name and describe 3 other operating systems. Include the type(s) of hardware they operate on.  Be careful not to use a Linux derivative or more than one from the same family of Operating Systems (eg Win8 and Win10 are in the same family). 

A multiprocessor with six processors has 16 attached DVD drives. There is a large number of jobs submitted to the system that each require a maximum of four DVD drives to complete execution. Assume that each job starts running with only three disk drives for a long period before requiring the fourth drive for a short period toward the end of its operation. Also assume an endless supply of such jobs.

1. a) Assume the scheduler in the OS will not start a job unless there are four DVD drives available. When a job is started, four drives are assigned immediately and are not released until the job finishes.
2. What is the maximum number of jobs that can be in progress at once? (2 marks)
3. What are the maximum and minimum number of DVD drives that may be left idle as a result of this policy? (2 marks)
4. b)  i. Suggest an alternative policy to improve DVD drive utilisation and at the same time avoid system deadlock. (2 marks)
5. What is the maximum number of jobs that can be in progress at once? (2 marks)
6. What are the bounds on the number of idling DVD drives? (2 marks)

1. a) Provide two examples of applications for which multi-threading provides better performance than a single-threaded solution. State your reasons. (4 marks)
2. b) Provide two examples of multi-threading applications where the threads should be implemented as pure kernel-level threads rather than pure user-level threads. State your reasons. Do not use examples from the textbook. (4 marks)

Write a short discussion, in your own words, on each of the following topics. The discussions, each in about 250 ± 50 words, should explain the meaning of the terms and concepts involved. You should give references for concepts, but you must use your own words. No marks will be awarded if your answer is similar to wordings used in your textbook or other available sources.

1. a) Process interaction and degree of awareness. (3 marks)
2. b) Mutual exclusion and the advantages of using semaphores compared to special machine instructions. (3 marks)

Task 1

Haiku Project

BeOS is an operating system which was created in the year 1991 besides latest version available is launched in 2001, subsequently the OS concluded to exist. Haiku a public motivated venture, is inclined through the BeOS besides have been developing ever since BeOS ended. This venture purpose is to have the OS to be well-suited with BeOS binaries. As this BeOS was enormously reactive as well as the correct quantity of structures in addition interactive UI. Haiku has similar features and hardware requirements are mentioned below:

• Ready processor of BeOS plus motherboard chipset.
• RAM required is 32mb
• SCSI or IDE hard disk
• SCSI or IDE/ATAPI D-ROM drive.
• VESA graphics.
• USB, Input device such as keyboard, mouse

(https://www.haiku-os.org/)

Originally this operating system was created by Microsoft and IBM teams. In the end, Microsoft team discontinued the partnership; however, IBM nonstop worked on this operating system. This operating system vied with Windows based OS such as MS-DOS. This operating system was used by some PCs and old ATM machines. At current time, IBM are not working on this OS, the ownership is now with Serenity Systems. Hardware used in this operating system is given below: 

• CPU: Intel Pentium 133 MHz
• Memory: 48 MB
• Video: PCI VGA video card with 512 kB .
• Drive : 500 MB
• SCSI or IDE CD-ROM drive

(https://www.ecomstation.com/demo.phtml?url=nls/en/content/requirements.html&title=System%20Requirements)

 SkyOS: The hobbyist developed this operating system. Thus, it is proprietary operating system instead of open source. The original SkyOS was obtainable after the payment. But in 2013 it was made available for free download to public. Hardware requirement for this shall be to have atleast 300 mb of ram to start with as 160mb was utilized for SkyOS.

A multiprocessor with six processors has 16 attached DVD drives. There is a large number of jobs submitted to the system that each require a maximum of four DVD drives to complete execution. Assume that each job starts running with only three disk drives for a long period before requiring the fourth drive for a short period toward the end of its operation. Also assume an endless supply of such jobs.

a) 

What is the maximum number of jobs that can be in progress at once? 

The maximum number of jobs that can be in progress at once can be 20/4 i.e. 5 jobs.

What are the maximum and minimum number of DVD drives that may be left idle as a result of this policy? (2 marks)

Subsequently single drive could be assigned to every procedure so minimum of one can be idle at a time, at most 5 drives shall be idle at a time.

b)  i. Suggest an alternative policy to improve DVD drive utilisation and at the same time avoid system deadlock. (2 marks)

To improve drive utilization, each process can be initially allocated with three tape drives, with the fourth drive allocated on demand.

What is the maximum number of jobs that can be in progress at once? (2 marks)

With this policy, at most ?20 / 3? = 6 processes can be active simultaneously.

What are the bounds on the number of idling DVD drives? (2 marks)

The minimum number of idle drives is 0 and the maximum number is 2.

a.

• A Register; each time a thing is checked the show must be refreshed to demonstrate the thing and the new aggregate cost and in addition the store stock level for that thing must be balanced. On the off chance that each of these undertakings is executed as its own string then regardless of the possibility that the call to the server to conform the store stock level is obstructed the whole procedure is not blocked, correspondingly while the screen is showing the thing name the processor can figure the aggregate and afterward show it. In this case, there are alot of calls to I/O gadgets so multithreading would be helpful so if a solitary I/O gadget is occupied the whole procedure is not blocked.
• Menu screen, each time a client chooses a menu choice that opens an alternate menu screen it could be opened as another procedure, leaving the first. However, the better choice is to open it as another string and put the primary screen's tread into a hold up status. Along these lines the processor is not swapping between procedures to such an extent and it is less demanding to bring a current string in those days make a procedure.

b.

• Example 1: At the point when a bit string endures a page blame, another bit string can be changed into utilization the interleaving time in a valuable way.
• Example 2:A multithreaded framework involving various client level strings can't make utilization of the diverse processors in a multiprocessor framework at the same time.

Process interaction and degree of awareness. 

A procedure is a program in execution. For instance, a running program picture is a solitary procedure of the working framework. The Multitasking Facility gives you a chance to isolate the program procedure into littler autonomous procedures that have a similar address space. We can make new procedures inside the program with help of function. The predicated process recognizes such procedures and these are divided into three phases of mindfulness as to its learning of different procedures.

1. In dispute
2. In a roundabout way, mindful of each other
3. Straightforwardly mindful of each other.

The methods for correspondence would be predicated by their capacity to detect each other. In 3^rd one, they could utilize post boxes or comparable develop to impart, in 2^nd one they would doubtlessly utilize shared items, in the company of first one they would battle for their assets through locks.

Anytime amid its execution, a procedure is in a specific state, as well as this state changes as the procedure runs. The condition of a procedure contains such data as the accompanying:

• the address of the following direction to be executed
• the estimations of uncommon and nearby factors
• the conditions under which the procedure can run
• the substance of the control stack
• the processor registers

For the reasons for this talk, the expression "prepare" alludes to a procedure in the Multitasking Facility; the expression "working framework handle" alludes to forms controlled by the working framework that runs the program.

1. Mutual exclusion and the advantages of using semaphores compared to special machine instructions. (3 marks)

A method for ensuring that if one procedure is utilizing a common modifiable information; alternate procedures will be rejected from doing likewise. Formally, while one process executes the common variable, every different procedure coveting to do as such in the meantime minute ought to be continued holding up; when that procedure has wrapped up the mutual variable, one of the procedures holding up; while that procedure has wrapped up the common variable, one of the procedures holding up to do as such ought to be permitted to continue. In this form, each procedure executing the common information rejects all others from doing as such at the same time and it is known as Mutual Exclusion.

When the code utilizes a semaphore to control access to a common variable, yet the semaphore could similarly also be utilized to control access to a mutual program. Since the underlying number in the semaphore is 1, the primary procedure to execute a hold up operation on that semaphore will be permitted into the basic area. While a procedure is in the basic area, then again, the incentive in the semaphore will be zero, driving different procedures to hold up. In the event, there are numerous mutual assets, each might be secured by a different semaphore. On the off chance that no procedure ever endeavors to utilize more than one shared asset at any given moment, this arrangement is sheltered and free of hazard. Then again, if at least two procedures must acquire select utilization of more than one asset eventually amid their execution, the utilization of isolated semaphores to monitor every asset may prompt gridlock.