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These are the Old Exam of Statistical Calcultions which includes Leaf Diagram, Frequency Distribution, Coefficient of Skewness, Third Quartile, Medical Expenses, Mean, Standard, Deviation, Cumulative Frequency etc.Key important poinst are:
Typology: Exams
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Instructions Answer any FOUR questions. All questions are worth equal marks.
Examiners: Mr. G. McSweeney Mr. J. Greenslade Mr. J. Walsh
(a) The command useradd can be used by an administrator to create a new user. How might the potential user be supplied with a password? Describe how the administrator might also provide the user with a home directory to store his/her files. Where might this home directory be placed? ( 7 Marks )
(b) Apart from using useradd , describe two other ways of creating a user account in a standard Linux distribution. ( 3 Marks )
(c) Explain how users are authenticated when they log in to a Linux system. In your answer consider password security. ( 5 Marks )
(d) KDE is a Linux graphical user interface, name another. ( 2 Marks )
(e) You are the root user of a Linux system which has a browser and a java compiler installed. The system has three ordinary users jane , bill and mary. Describe how you might grant jane and mary read and execute permissions for the browser and how you might grant jane and bill read and execute permission for the compiler. The user mary should not have any permissions for the compiler and the user bill should not have any permissions for the browser. ( 8 Marks )
(a) Describe the difference between a pre-emptive and a non pre-emptive scheduling algorithm. ( 2 Marks )
(b) Give one example of a pre-emptive scheduling algorithm and one example of a non pre-emptive scheduling algorithm. ( 2 Marks )
(c) Consider the following set of processes with duration given in milliseconds.
Process Name Arrival Time Service Time P1 0 3 P2 2 6 P3 4 2 P4 5 1
Draw a time line to show the execution of each of these processes for the (^) Round Robin algorithm
(time slice = 2 milliseconds). Calculate the Turnaround Time and Normalised Turnaround
Time. ( 7 Marks )
(d) Describe the following methods of disk space allocation. In your answer state any advantages and disadvantages of each:
(f) For the following track request queue, calculate the head movement required for each of the following disk scheduling algorithms. Assume that the head starts at track 152 and is moving toward track 199. Also assume that the drive has 200 tracks numbered 0-199.
Request queue: 86, 147, 91, 177, 94, 150, 102, 175, 130
(i) Scan ; (ii) Shortest Seek Time First. ( 6 Marks )
(a) Write a shell script which automatically archives, compresses and backs up the contents of your home drive to a zip disk. Assume the zip disk is already mounted and its main directory is at /media/zip. ( 9 Marks )
(b) Write a complementary script which retrieves the compressed and archived files in (a) above. ( 7 Marks )
(c) How would you grant yourself permission to execute the scripts? ( 2 Marks )
(d) Write an interactive shell script which has the following output:
The user is prompted to enter an integer ( 1 to (^) 4 ) and the script responds appropriately e.g. if the
user enter (^) 3 the current (^) date and (^) time are displayed. ( 7
Marks )
(a) State four advantages of using UNIX. ( 4 Marks )
(b) State two disadvantages of using UNIX. ( 4 Marks )
The following is a long list of a UNIX file. Explain the purpose of each of the fields in the list:
-rw-r--r-- jane its2005 346 Feb 1 15:31 outFile ( 6 Marks )
(c) Describe – with the aid of a diagram - how UNIX allocates disk space. In your answer consider how it copes with both large and small files. ( 8 Marks )
(d) Compare the UNIX disk space allocation method with the contiguous allocation method. ( 3 Marks )