Consider three processes are represented by programs that are fully loaded in main memory. In addition, there is a small dispatcher program that switches the processor from one process to another. The table below shows the traces of each of the processes during the early part of their execution. The first 12 instructions executed in processes A and C are shown. Process B executes four instructions, and we assume the fourth instruction invokes an I/O operation for which the process must wait. The same sequence of instructions is executed by the dispatcher in each instance because the same functionality of the dispatcher is being executed. We assume the OS only allows a process to continue execution for a maximum of four instruction cycles, after which it is interrupted; this prevents any single process from monopolizing processor time. The dispatcher executes four instructions before turning control to the process.

1. Show the interleaved traces resulting from the instruction cycles.

2. Draw the process states for the trace given above.

5000=5000= Starting address of program of process A

8000=8000= Starting address of program of process B

12000=12000= Starting address of program of process C

(a) Trace of process A(b) Trace of process B(c) Trace of process C

5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011

8000 8001 8002 8003

12000 12001 12002 12003 12004 12005 12006 12007 12008 12009 12010 12011