Operating Systems Assignment 1

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CS 3305A: Operating Systems

Assignment 1

Purpose
The goals of this assignment are the following:
• Gain more experience with the C programming language from an OS perspective
• Get experience with the fork(), wait(), execl(), execlp(), and pipe()system functions
Part I: Parent and Child Processes (50 points)
Write a program in C that will perform the following tasks:
1. Your program will create a parent process which will create two child processes (e.g., child_1,
and child_2)
2. parent will wait for child_1 to complete before creating child_2
3. child_1 will create its own child child_1.1
4. Inside child_2, a system call to an external program will be made (let’s say this external
program is “external_program.out” that prints “Hello World”), and as a result of this external
program call, child_2 will be replaced by external_program.out (hint: execl())
The expected output from your program should look like the following:
parent process (PID 2255) created child_1 (PID 2256)
parent (PID 2255) is waiting for child_1 (PID 2256) to complete before creating child_2
child_1 (PID 2256) created child_1.1 (PID 2257)
child_1 (PID 2256) is now completed
parent (PID 2255) created child_2 (PID 2258)
child_2 (PID 2258) is calling an external program external_program.out and leaving child_2…
From the external program: Hello World..
Your submission file must be assignment1_part1.c.
Hints: fork(), wait(), getpid(), getppid(), execl()
Part II: Inter-Processes Communications (50 points)
Write a C program that will accept two integer values from the user as command line arguments
(for example, X and Y). Your program will create a parent and child where the parent process will
read X and the child process will read Y. Now, child process will send Y to parent process by
communicating parent process through a pipe (i.e., shared memory). Then the parent process will
add Y to X and produce the sum. The expected output from your program should look like the
following:
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1. A pipe is created for communication between parent (PID 2255) and child
2. parent (PID 2255) created a child (PID 2256)
3. parent (PID 2255) Reading X = 10 from the user
4. child (PID 2256) Reading Y = 20 from the user
5. child (PID 2256) Writing Y into the pipe
6. parent (PID 2255) Reading Y from the pipe (Y = 20)
7. parent (PID 2256) adding X + Y = 30
Your submission file must be assignment1_part2.c.
Hints: fork(), wait(), getpid(), getppid(), pipe(), write(), read()
Mark Distribution
This section describes a tentative allocation of marks assigned for the desired features.
• Part I: Parent and Child Processes (50 points)
a) A Parent process will create two Child processes: 10 points
b) Child_1 will create its own child Child_1.1: 10 points
c) Parent will wait for Child_1 to complete before creating Child_2: 10 points
d) Child_2 will make a system call to external_program.out: 20 points
• Part II: Inter-Processes Communications (50 points)
a) Parent reads X from user: 5 points
b) Child reads Y from user: 5 points
c) A pipe is created for communication between Parent and Child: 15 points
d) Child writes Y into the pipe: 10 points
e) Parent reads Y from the pipe: 10 points
f) Parent adding two variables X+Y: 5 points
Assignment computing platform
Please visit the course website for assignment related specific technical instructions (Assignment
submission, Assignment computing platform, relevant materials etc.). Also, consult TAs, and
Instructor for any question you may have regarding this assignment.