L-1.9: Questions on Fork System Call With Explanation | Operating System

Summary

In this video, the presenter explains the Fork() system call in C programming, focusing on the creation of parent and child processes. The video covers how Fork() generates a child process and how both processes execute concurrently. It discusses key concepts such as the return values of child (0) and parent (positive number) processes, and how logical operators like '&' affect execution flow. The tutorial provides a detailed breakdown of how these processes interact and prints 'Hello' multiple times, emphasizing the importance of understanding Fork() for solving competitive exam questions.

Takeaways

• 😀 The Fork() system call is essential for parallel processing, creating both parent and child processes.
• 😀 The parent process executes separately from the child process, both running concurrently.
• 😀 The value returned by Fork() is 0 for the child process and a positive number for the parent process.
• 😀 The `&` operator in Fork() ensures that both the first and second conditions are evaluated before execution.
• 😀 If the first value in the `&` operator is true, it will evaluate the second value to determine whether to execute the following statement.
• 😀 The child process, when evaluated with the `&` operator, will return 0, which leads to a 'false' condition, skipping the fork in the child process.
• 😀 In the parent process, the positive value returned by Fork() means a 'true' condition, allowing the execution of the following fork statement.
• 😀 When both the parent and the second child process (created by the parent) print 'Hello', the total number of prints is four.
• 😀 Understanding the return values of Fork() is crucial: the child always returns 0, and the parent always returns a positive number.
• 😀 It's important to understand how the number of Fork() executions and the logical operators used (such as `&` and `||`) affect the program's flow.
• 😀 The use of logical operators (`&` vs. `||`) can change the behavior of Fork() in the program and lead to different outcomes in terms of process execution.

Q & A

What is the main topic of this video?

The main topic of the video is understanding how the `fork()` system call works in C programming, especially in the context of concurrent execution and process creation.

What is the significance of the `fork()` system call?

The `fork()` system call is used to create a new process by duplicating the calling (parent) process. This results in two processes running concurrently: the parent and the child.

What is the role of the parent and child processes in the script?

The parent process runs first, and after calling `fork()`, it creates a child process. The parent process continues execution independently, while the child process starts running from the point where `fork()` was called, but it has a different return value.

What is the return value of `fork()` for the parent and child processes?

For the child process, `fork()` returns 0, and for the parent process, it returns a positive number, usually 1 or any positive integer.

How does the logical operator `&` behave in the context of `fork()`?

The `&` operator is a bitwise AND operator. In the script, it ensures that both the parent and child processes must meet certain conditions before executing the code inside the `if` statement. The first value must be true (non-zero) for the second condition to be evaluated.

What is the difference between using `&` and `|` operators with `fork()`?

Using `&` (AND operator) ensures that both conditions must be true for the code to execute. In contrast, using `|` (OR operator) would allow the code to execute if either condition is true.

Why does the child process print 'Hello' only once?

The child process prints 'Hello' only once because it evaluates the first `fork()` return value as 0, which leads to a false condition in the `if` statement, skipping the second `fork()` call and directly executing the `printf` statement.

Why does the parent process end up printing 'Hello' twice?

The parent process prints 'Hello' twice because after the first `fork()`, it returns a positive value, which allows the second `fork()` to execute, creating a second child that prints 'Hello'.

How many times is 'Hello' printed in total?

The 'Hello' statement is printed a total of four times. The child process prints it once, while the parent process prints it twice (once from its own execution and once from the second child it creates).

What key point should you remember when solving `fork()` questions?

You should remember that the child process always returns 0, and the parent process always returns a positive number. Additionally, the number of `fork()` calls made determines how many processes are created and how many times output like 'Hello' is printed.