Operating Systems - Prof. Omar Mansour

New York University

Tandon School of Engineering

Department of Computer Science and Engineering

Introduction to Operating Systems

Spring 2025

Assignment 5

(10 points)

A) (7 points) Write a program whose main routine obtains two parameter n and d from the user (i.e., passed to

your program when it was invoked from the shell, n>1). Your program shall then create a shared memory and

a child process. The shared memory shall have a size of BUF_SZ*sizeof(int), where BUF_SZ is

defined as 5 using a macro, e.g. “#define BUF_SZ 5”.

The child process should obtain the values of n and d from the parent (you actually have multiple options for

doing that) and create (but not print) an arithmetic sequence of length n and whose elements are of type

int, such that each element has a value of kd, where k is the element number (0 to n-1). For example, if

n=5 and d=2, the sequence shall be 0,2,4,6 and 8.

The child process shall create the elements, one at a time, and wait for a random interval of time ( 0 <= time <

3 seconds) between generating elements of the sequence. As soon as an element is generated, the child

places the element in the shared memory by organizing it into a fixed-size shared buffer that implements a

producer-cosumer queue as described in the lectures.

The parent process shall print elements it receives on the shared buffer immediately as soon as they arrive,

without waiting for the child process to exit.

Note: For this assignment, you may or may not use a virtual file to create the shared memory (i.e.

anonymous vs named shared memory). Both methods will work fine since the processes have a parent-child

relationship. But if you use a virtual file to create a shared memory, you should delete your virtual file (using

unlink() ) prior to both processes exiting. For our usage in this assignment, you do the unlink only

once, such that one process creates the virtual file and the other deletes it.

The reason why deleting a file (virtual or real file) is referred to as unlink will be clarified towards the final

week of this course, when we discuss filesystems.

Hint: Use fflush() to ensure printf’s are printed immediately into the screen.

B) (3 points) Repeat part A, except that now you do not create a shared memory, but rather use an ordinary pipe

to pass the sequence (multiple ways of passing n and d, as in part A).

What to submit to gradescope:

Please submit the following files individually:

Operating Systems - Prof. Omar Mansour

1) Source file(s) with appropriate comments.

The naming should be similar to “lab#_$.c” (# is replaced with the assignment number and $ with the

question number within the assignment, e.g. lab4_b.c, for lab 4, question b OR lab5_1a for lab 5, question

1a).

2) A single pdf file (for images + report/answers to questions), named “lab#.pdf” (# is replaced by the

assignment number), containing:

• Screen shot(s) of your terminal window showing the current directory, the command used to

compile your program, the command used to run your program and the output of your program.

3) Your Makefile, if any. This is applicable only to kernel modules.

RULES:

• You shall use kernel version 4.x.x or above. You shall not use kernel version 3.x.x.

• You may consult with other students about GENERAL concepts or methods but copying code (or code

fragments) or algorithms is NOT ALLOWED and is considered cheating (whether copied form other

students, the internet or any other source).

• If you are having trouble, please ask your teaching assistant for help.

• You must submit your assignment prior to the deadline.