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Operating Systems (CS C372) Test #1 1

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI

First Semester 2003-2004

Course Title : OPERATING SYSTEMS Course No CS C372

Component : Test I (Regular) Open Book Component 

Weightage : 15% Max Marks: 15 Date: 27/09/2004

Note: Attempt all the Questions. Start each answer from a fresh page.

Question #1 (5 Marks)A multilevel feedback queue algorithm works with the following condition

Number of queues 3 + 1 Auxiliary Queue (Q1, Q2 and Q3)

Scheduling algorithm Q1 uses Virtual Round Robin, Q2 uses Round Robin

Q3 uses Highest Response Ratio Next

Method used to upgrade a process No upgrading among queues

Method to demote a process Q1After 6 units of time (Quantum time 6), Q2 After 6 units of 

time (Quantum time 6)(if preempted in Q2 the process will continue remain in the front of the queue till the

quantum time expiry), Q3Highest Response Ratio process in the queue will get the first chance.

Method used to determine which queue a process will enter

P1, P3 & P4 are entering through Queue #1 (Q1), P2 is entering through Queue #2 (Q2)

Process Total CPU burst CPU burst I/O burst Arrival time

P1 32 16 6 0P2 26 10 4 1

P3 10 3 15 2

P4 32 14 1 5

Calculate Average waiting time, average turn around time, and CPU utilization

Question #2 (2 Marks)(a) Briefly explain the major differences between a client communicating with a server via message

passing and via remote procedure calls (RPCs).

(b) Select those items in the list below that a thread shares with other threads in the same process.

(a) Address space (b) Heap (c) Program counter

(d) Files (e) Local variables registers

(f) Global variables (g) Program code (h) Stack pointer

Question #3 (3 Marks)Find the number of new processes created.

void main() {

int i;

for(i=0;i<=1;i++) {

fork();

if(!fork()) {

fork();

execl(“/bin/ls”,”ls”,NULL);

fork();

}

fork();

}fork();

}

Question #4 (3 Marks)The letters A, B in the following program represents some C statements.

#include <stdio.h>

void main( int argc, char *argv[] ) {

int i,p[2];

for( i=1; i<= argc-2; i++ ) {

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Operating Systems (CS C372) Test #1 2

pipe(p);

if ( fork( ) ) { A } else { B }

}

}

The program is to be run with k arguments as ./a.out a1 a2 a3 ……. ak 

For each of the following A and B, determine if the program implements one of 

a1 | a2 | a3 | …… | ak,

ak | ……. | a3 | a2 | a1,

ak | a1,

a1 | ak 

or none of these pipes

(a) If A is

dup2 ( p[0], fileno ( stdin ) ); close ( p[0] ); close ( p[1] ) ;

B is

dup2 ( p[1], fileno ( stdout ) ); close ( p[0] ); close ( p[1] ) ;

execlp ( argv[i], argv[i], ( char * ) 0 );

The program implements__________________

(b) If A is

dup2 ( p[0], fileno ( stdin ) ); close ( p[0] ); close ( p[1] ) ;

execlp ( argv[i], argv[i], ( char * ) 0 );

B isdup2 ( p[1], fileno ( stdout ) ); close ( p[0] ); close ( p[1] ) ;

The program implements __________________

(c) If A is

dup2 ( p[1], fileno ( stdout ) ); close ( p[0] ); close ( p[1] ) ;

B is

dup2 ( p[0], fileno ( stdin ) ); close ( p[0] ); close ( p[1] ) ;

execlp ( argv[i], argv[i], ( char * ) 0 );

The program implements__________________

(d) If A is

dup2 ( p[1], fileno ( stdout ) ); close ( p[0] ); close ( p[1] ) ;

execlp ( argv[i], argv[i], ( char * ) 0 );

B is

dup2 ( p[0], fileno ( stdin ) ); close ( p[0] ); close ( p[1] ) ;The program implements __________________

Question #5 (2 Marks)Consider the following program

#define _REENTRANT

#include <stdio.h>

#include <pthread.h>

int turn = 10;

void * many ( void * arg ) {

pthread_t tid;

if ( - - turn > 0) {

printf(“ %d\t”, turn );

pthread_create ( &tid, NULL, many, ( void * ) 0);pthread_join( tid, NULL );

}

}

int main( ) {

many ( NULL ) ;

return 0;

}Find all the output sequences (Including duplications if any), if the threads are following FCFS

scheduling. pthread_join will push the thread to waiting state.