Suppose in a multiprogramming environment, the following C program segment is executed. A process goes into I/O queue whenever an I/O related operation is performed. Assume that there will always be a context switch whenever a process requests for an I/O, and also whenever the process returns from an I/O. The number of times the process will enter the ready queue during its lifetime (not counting the time the process enters the ready queue when it is run initially) is ___________ . Answer in integer)
int main()
{
int x=0,i=0;
scanf("%d",&x);
for(i=0; i<20; i++)
{
x = x+20;
printf("%d\n",x);
}
return 0;
}
View worked solution
Answer: 21:21
To find the number of times the process enters the ready queue during its lifetime (excluding the initial entry), we analyze the I/O operations in the program segment:
- Input Operation (
scanf): The statementscanf("%d", &x);is executed once. This triggers an I/O request, moving the process to the I/O queue. When this I/O completes, the process returns from I/O and enters the ready queue.
Ready queue entries fromscanf= 1 - Output Operations (
printf): Theforloop runs exactly 20 times (for ). In each iteration, the statementprintf("%d\n", x);is executed. Eachprintfis an I/O operation that moves the process to the I/O queue. Upon completion of each print operation, the process enters the ready queue.
Ready queue entries fromprintf= 20
Summing these up, the total number of times the process enters the ready queue after completing an I/O operation is:
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