Each section shows how several process scheduling algorithms would execute the processes.
This policy services processes in the order they start.
process name  arrival time  service time  start time  finish time  turnaround time  waiting time  response time 

A  0  10  0  10  10  0  1.0 
B  1  29  10  39  38  9  1.3 
C  2  3  39  42  40  37  13.3 
D  3  7  42  49  46  39  6.6 
E  4  12  49  61  57  45  4.8 
mean  38.2  26  5.4 
In what follows, the number in parentheses in the comment field is the remaining service time for the process. In order of execution:
time  ready queue  comments 

0  A  A(10) arrives, runs 
1  AB  B(29) arrives, A(9) is not interrupted and continues to run 
2  ABC  C(3) arrives and is appended to the queue; again, A(8) continues to run 
3  ABCD  D(7) arrives and is appended to the queue; again, A(7) continues to run 
4  ABCDE  E(12) arrives and is appended to the queue; again, A(6) continues to run 
10  BCDE  A finishes, B(29) runs 
39  CDE  B finishes, C(3) runs 
42  DE  C finishes, D(7) runs 
49  E  D finishes, E(12) runs 
61  —  E finishes 
This policy services the process with the shortest service time next. It is sometimes also called “shortest job next” (SJN).
process name  arrival time  service time  start time  finish time  turnaround time  waiting time  response time 

A  0  10  0  10  10  0  1.0 
B  1  29  32  61  60  31  2.1 
C  2  3  10  13  11  8  3.7 
D  3  7  13  20  17  10  2.4 
E  4  12  20  32  28  16  2.3 
mean  25.2  13  2.3 
In what follows, the number in parentheses in the comment field is the remaining service time for the process. In order of execution:
time  ready queue  comments 

0  A  A(10) arrives, runs 
1  AB  B(29) arrives, A(9) continues to run 
2  ABC  C(3) arrives and is appended to the queue; again, A(8) continues to run 
3  ABCD  D(7) arrives and is appended to the queue; again, A(7) continues to run 
4  ABCDE  E(12) arrives and is appended to the queue; again, A(6) continues to run 
10  BCDE  A finishes; C(3) has the shortest service time, so it runs 
13  BDE  C finishes, D(7) has the shortest service time, so it runs 
20  BE  D finishes, E(12) runs 
32  B  E finishes, B(29) runs 
61  —  B finishes 
This policy services the process with the shortest service time next. It is sometimes also called “preemptive shortest job next” (PSJN).
process name  arrival time  service time  start time  finish time  turnaround time  waiting time  response time 

A  0  10  0  2  preempted by C  
8  12  20  20  10  2.0  
B  1  29  32  61  60  31  2.1 
C  2  3  2  5  3  0  1.0 
D  3  7  5  12  9  2  1.3 
E  4  12  20  32  28  16  2.3 
<mean>  24  11.8  1.7 
In what follows, the number in parentheses in the comment field is the remaining service time for the process. In order of execution:
time  ready queue  comments 

0  A  A(10) arrives, runs 
1  AB  B(29) arrives; as its service time is greater than that of A(9), B is appended to the queue and 
A continues to run  
2  CAB  C(3) arrives; as its service time is less than that of A(8), C runs. A’s service time is less than 
that of B(29), so it goes before B in the queue  
3  CDAB  D(7) arrives; as its service time is greater than that of C(2), D is placed in the queue at the 
appropriate place, and C continues to run  
4  CDAEB  E(12) arrives; as its service time is greater than that of C(1), E is placed in the queue at the 
appropriate place, and C continues to run  
5  DAEB  C finishes; D(7) has the shortest remaining service time, so it runs 
12  AEB  D finishes, A(8) has the shortest remaining service time, so it runs 
20  EB  A finishes, E(12) has the shortest remaining service time, so it runs 
32  B  E finishes, B(29) has the shortest remaining service time, so it runs 
61  —  B finishes 
This policy services the process with the greatest (highest) response ratio next.
process name  arrival time  service time  start time  finish time  turnaround time  waiting time  response ratio 

A  0  10  0  10  10  0  1.0 
B  1  29  32  61  60  31  2.1 
C  2  3  10  13  11  8  3.7 
D  3  7  13  20  17  10  2.4 
E  4  12  20  32  28  16  2.3 
mean  25.2  13  2.3 
In order of execution:

ECS 150, Operating Systems Version of April 17, 2022 at 9:03PM

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