In-class activity 1

Question 1

Give one example of fork() in common applications

Answer 1

• when we double-click on an icon, a program (new process) opens in a new window
• running a sub-process on a shell creates a new command with a fork

Question 2

when a process is created using fork(), the ____ is not inherited by the child process

Answer 2

• process id
• parent’s list of file descriptor

Question 3

what happens if you call exec before fork in a shell

Answer 3

the code doesn’t work because the shell’s address space is replaced with the exec’s command, and the shell will terminate once the command is terminated

Question 4

how is a system call different from a typical procedure call

Answer 4

system calls have a mode switch from user mode to kernel mode

Question 5

Assume that the root process has pid = 1000; what can you say about the pid of a child?
a) It will be greater than 1001
b) Any number greater than 1000
c) It Could be any random number.

Answer 5

Any random number

limit on the maximum number of pids, they will be reused after a certain time

Question 6

If we put the parent process to sleep, and meanwhile, the child process exits. What will happen in this scenario?

Answer 6

The child will become a zombie process (A process that has finished the execution but still has an entry in the process table to report to its parent process)

Question 7

what is the purpose of calling wait(NULL) instead of wait()

Answer 7

wait(null) blocks the parent process until any of its children exit, otherwise the child might become an orphan process

Question 8

do changes of a global variable in a parent process change the variable in the child process

Answer 8

no, they both have their own copies

Question 9

Fill in the correct boolean expression to complete the fragments.
if ( … )
printf( “I am not an orphan child \n” );

Answer 9

getppid() != -1