Os doubt fork related

Question

the output of the following program is

Void main()

{

Int a= 10;

If (fork()==0)

a++;

Print("%d", a);

}

 

0,10

10,10

11,10

11,11

Comments

One parent and child process are created.

Parent will print 10 and again when child is called a is incremented to 11(post increment)  thatswhy 11 is printed.

Correct if I m wrong...

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For pre increment in program will it be

11 for parent

12 for child or 11 for both...

I m very confused...:(

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Yes correct 11 11 is not at all possible because parent will never enter if loop and thus one value will definitely one short than other now it depends on implementation if wait call is implemented then child will print first which is incremented value and getting return call parent will print : 11,10 
The second scenario could be without wait call in which both process can print randomly one after other .
So one more possibility 10,11. Thus question suppose wait is implemented.
Wait call reference: http://www.csl.mtu.edu/cs4411.ck/www/NOTES/process/fork/wait.html

Answer 1

When ever fork system call is executed parent and child have create there local copy of variable, so both will have value a=10, now when child copy is executed it will increase value of it, but this change is within child's own address space so answer will be

Either 10,11 or 11,10 it depends if Who will execute first

Since only one option match this final Answer is 11,10

Comments

 Tesla! Arjun sir

when fork() system call is invoked it returns a process id of  the child process in the parent process,and zero value for the child process

then it should be 0,10 ?

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fork system call can return atmost 2 values

on successful implementation it return a non zero value to parent and zero to child, so parent in it user space will executed only printf but for child PID is zero so when child process will execute it will increment a and then print.

@set2018 why 0 will be printed ?

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 why 0 will be printed ?

 for child PID is zero

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Where in code we are printing PID? We are printing vale of a which has nothing to do with PID