Operating Systems

Course information

Instructor: Yang Tang.
Semester: Fall 2022.
Outline: High-level design of key operating system concepts using Linux as an example; Process scheduling, process synchronization; Deadlocks and their prevention; I/O, file systems; Memory management, paging, segmentation; Security and protection.
Programming Language: C.

Gradebook

Overall grade: A (4.00/4.00)

Item	Grade	Letter
Assignments	10/10	A
Labs	48.5/50	A
Midterm	89.5/101	A
Final	82/100	A

Labs

Lab 2: nyush

Shell-nyush, a.k.a. New Yet Usable Shell, is an implementation of a simple version of the Linux shell. It is an interactive command-line program, involving process creation, destruction, and management, signal handling, and I/O redirection. Basic functionality include:

Program locating and execution.
Process termination and suspension.
Signal handling.
I/O redirection (including piping).
Built-in commands (including cd, exit, jobs, and fg).

These are some example usages of nyush.

You may access the source code here, and note that you should run it in a Linux environment.

Lab 3: nyuenc

Encoder-nyuenc, a.k.a. Not Your Usual Encoder, is an implementation of a parallelized run-length encoding (RLE). Multiple threads are created to encode in parallel, leading to better performance. In order to avoid frequent creation and destruction of threads, a thread pool is implemented to maintain a certain number of threads, specified by a flag. POSIX threads is used in this lab, and mutual exclusions and conditional variables are used for elimination of race conditions. Basic functionality include:

Supports a -j flag. If specified, the corresponding number of threads will be initialized in a thread pool. Otherwise, the encoding will be done sequentially.
Implements run-length encoding (RLE).
Free of race conditions or busy waiting among threads to achieve high and stable parallelization.

Some benchmarking statistics are shown as follows:

Size (MB)	Threads	Time (s)
100	1	2.982
100	3	1.026
1000	3	5.206

You may access the source code here, and note that you should run it in a Linux environment.

Lab 4: nyufile

FileRecovery-nyufile, a.k.a, Need You to Undelete My File, is a program for recovering deleted files in a FAT32 file system. Its usage is as follows:

Usage: ./nyufile disk <options>
    -i                          Print the file system information.
    -l                          List the root directory.
    -r filename [-s sha1]       Recover a contiguous file.
    -R filename -s sha1         Recover a possibly non-contiguous file.

Basic functionality include:

Adapts to different configurations of FAT32 disks.
Provides reliable file recovery as long as the file contents are not rewritten.
Searches by file size for contiguously allocated fata blocks and recovers the file.
Searches by brute force permutation for non-contiguously allocated data blocks given the SHA1 hash of the file contents and recovers the file.

You may access the source code here, and note that you should run it in a Linux environment.