Process creation (fork and exec) in Operating Systems - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the fork() system call do in process creation?

The fork() system call creates a new process by duplicating the calling process. The new process is called the child process, and it is almost an exact copy of the parent process.

beginner

What is the purpose of the exec() family of functions?

The exec() functions replace the current process's memory and code with a new program. This means the process starts running a different program without creating a new process.

intermediate

How do fork() and exec() work together in creating a new process?

First, fork() creates a copy of the current process. Then, the child process uses exec() to replace its code with a new program. This way, a new process runs a different program.

intermediate

What is the difference between the parent and child process after a fork() call?

After fork(), both processes run independently. The parent gets the child's process ID as the return value, while the child gets zero. They have separate memory spaces but start as copies.

advanced

Why is fork() considered a cheap operation in modern operating systems?

Because modern OS use 'copy-on-write', which means the actual copying of memory happens only if either process changes it. This saves time and memory when creating new processes.

What does the fork() system call return to the child process?

A -1

B Child's process ID

C Parent's process ID

D 0

The fork() call returns 0 to the child process and the child's process ID to the parent.

Which system call replaces the current process's program with a new one?

A exec()

B exit()

C wait()

D fork()

exec() replaces the current process's code and memory with a new program.

What happens if fork() fails?

A Returns -1

B Returns child's PID

C Returns 0

D Creates a zombie process

If fork() fails, it returns -1 indicating an error.

Why do operating systems use copy-on-write with fork()?

A To speed up process termination

B To share memory permanently

C To avoid copying memory until necessary

D To prevent process creation

Copy-on-write delays copying memory until either process modifies it, saving resources.

Which of these is true about the child process after fork()?

A It immediately runs a different program

B It runs the same program as the parent initially

C It shares the same memory space as the parent

D It cannot execute <code>exec()</code>

After fork(), the child runs the same program as the parent until it calls exec() or exits.

Explain how fork() and exec() work together to create a new process running a different program.

Think about copying first, then replacing the program.

Describe what happens in the system when fork() is called and why copy-on-write is important.

Focus on memory handling after fork.