Andrew S. Tanenbaum (OS) Edition 4 Exercise 2 Question 39 (Page No. 177)

Question

Consider the following piece of C code:
 

void main( ) {

      fork( );
      fork( ); 
      exit( ); 

} 

How many child processes are created upon execution of this program?

Answer 1

Given statements ,

1. void main( ) {
2.       fork( );
3.       fork( );
4.       exit( );
5. }

At line #2,

           one child process will be created.

Now we have total 2 processes, 1 child process and another parent,

And the next statement to execute is line#3 in both processes.

 

At line #3

Now both processes(1 parent and 1 child process)  executes line#3 ,  and this will create two child processes.

One created by parent , And another by child (which was earlier created at line #2).

So,

total child processes are 1(line#2) + 2(line#3) → 3 child processes

 

 

General formula for calculating no. of child processes  (2^n) -1  (unless the fork is not called upon any condition)

Answer 2

2^2-1 =3

Hence ans : 3

Answer 3

yes  i am agree  with that fork is always creted process 2^n-1.(where n is the number of fork ()) and  finaly put the value of n and calculated the number of  child process … so calculated  answer is 3..

Answer 4

n=no of fork call

formula = 2^n-1