Using the process state diagram, explain why there is no transition:
• From the READY to WAITING.
• From the WAITING to RUNNING.

CS323: Case Study 3

a. Job1 (100k) f. Job6 (6k)

turnaround: 3 turnaround: 1

 

b. Job2 (10k) g. Job7 (25k)

turnaround: 1 turnaround: 1

 

c. Job3 (35k) h. Job8 (55k)

 

turnaround: 2 turnaround: 2

 

d. Job4 (15k) i. Job9 (88k)

 

turnaround: 1 turnaround: 3

 

e. Job5 (23k) j. Job10 (100k)

 

turnaround: 2 turnaround: 3

 

*turnaround – how long it will stay in the memory.

Instructions:

a. Job1 (100k) f. Job6 (6k)

turnaround: 

3 turnaround: 1

 

b. Job2 (10k) g. Job7 (25k)

turnaround: 1 turnaround: 1

 

c. Job3 (35k) h. Job8 (55k)

 

turnaround: 2 turnaround: 2

 

d. Job4 (15k) i. Job9 (88k)

 

turnaround: 1 turnaround: 3

 

e. Job5 (23k) j. Job10 (100k)

 

turnaround: 2 turnaround: 3

 

*turnaround – how long it will stay in the memory.

Instructions:

CS323: Case Study 2

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems. Name at least two of these problems. Can we ensure the same degree of security in a time-share machine as we have in a dedicated machine? Explain your answer Instructions:

Multiprogramming is a rudimentary form of parallel process in which several programs are run at the same time on a uniprocessor. Since there is only one processor, there can be no true simultaneous execution of different programs. Instead, the operating system executes part of one program, then part of another, and so on. To the user it appears that all programs are executing at the same time.

- Multiprogramming is different from the multiprocessing because even though there may be several programs currently active, the uniprocessor is not simultaneously executing commands for all the programs. Instead, the processor addresses each program, executes a single command, then moves on to the next program in the queue. The previous program remains active, but enters into a passive state until the uniprocessor returns to the front of the queue and executes a second command.

Time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.

 - Example of multiprogramming and time-sharing - printers that is connected with the system. State that a certain user is asking the attendant to print a certain file form his unit. The file now is being printed. There comes another user that hit’s the print button, so the file is being processed to be printed. It will interrupt the current printing process. It will cause the printer to mix output in printing the data because the other user is now printing his own file. Because they also share system resources, it will interrupt other current processing files.

Various security problems

-  One user can copy another user's program / memory space. This could be very detrimental if, for example, an administrator was running a decryption protocol, and another user stole the decryption program and/or key.

-  Resource usage may not be completely controlled, and could cause deadlock for certain users. For example, if user A had resource 1 and was waiting for resource 2, and user B had resource 2 and was waiting for resource 1, deadlock would occur and neither user would be able to make progress in their program, no matter how many time slots they were allocated.

We can’t ensure that the same degree of security in a time-share machine. Time-shared machines are far less secure; it steals or copies one’s program to data or its memory space, and is very easy to overload the buffers. Also they are much slower to catch a virus.

Dedicated machine built into another device for the purpose of controlling or supplying information to it. Its use has increased dramatically since the advent of the microprocessor: washing machines, cars, and MP3 players, etc. all have their own processors.

CS323: Case Study 2

In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems. Name at least two of these problems. Can we ensure the same degree of security in a time-share machine as we have in a dedicated machine? Explain your answer Instructions:

Multiprogramming is a rudimentary form of parallel process in which several programs are run at the same time on a uniprocessor. Since there is only one processor, there can be no true simultaneous execution of different programs. Instead, the operating system executes part of one program, then part of another, and so on. To the user it appears that all programs are executing at the same time.

- Multiprogramming is different from the multiprocessing because even though there may be several programs currently active, the uniprocessor is not simultaneously executing commands for all the programs. Instead, the processor addresses each program, executes a single command, then moves on to the next program in the queue. The previous program remains active, but enters into a passive state until the uniprocessor returns to the front of the queue and executes a second command.

Time-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.

 - Example of multiprogramming and time-sharing - printers that is connected with the system. State that a certain user is asking the attendant to print a certain file form his unit. The file now is being printed. There comes another user that hit’s the print button, so the file is being processed to be printed. It will interrupt the current printing process. It will cause the printer to mix output in printing the data because the other user is now printing his own file. Because they also share system resources, it will interrupt other current processing files.

Various security problems

-  One user can copy another user's program / memory space. This could be very detrimental if, for example, an administrator was running a decryption protocol, and another user stole the decryption program and/or key.

-  Resource usage may not be completely controlled, and could cause deadlock for certain users. For example, if user A had resource 1 and was waiting for resource 2, and user B had resource 2 and was waiting for resource 1, deadlock would occur and neither user would be able to make progress in their program, no matter how many time slots they were allocated.

We can’t ensure that the same degree of security in a time-share machine. Time-shared machines are far less secure; it steals or copies one’s program to data or its memory space, and is very easy to overload the buffers. Also they are much slower to catch a virus.

Dedicated machine built into another device for the purpose of controlling or supplying information to it. Its use has increased dramatically since the advent of the microprocessor: washing machines, cars, and MP3 players, etc. all have their own processors.