Caltech CS 124 Operating Systems

Building an operating system on Pintos (equivalent to Stanford's CS 140).

Project 1: Command Shell

• Parses a user command
• Handles forking and input/output redirection and piping
• Executes the command in a user program simulating the shell

Project 2: PC Booter

• Bootloader (written in IA32 assembly) loads a Pong game (written in C) into memory
• Transitions from real to protected mode and calls the entry to the Pong game
• Pong game utilizes ASCII for video output and timer & keyboard interrupts for state updates

Project 3: Threads

• Implements lazy waiting for timer sleeps
• Implements priority scheduling for threads and priority donation for locks
• Implements a multilevel feedback queue scheduler (similar to 4.4BSD scheduler)

Project 4: User Programs

• Implements argument passing for user programs
• Reads from user memory and handles errors and denies writes to executables
• Implements basic system calls (halt, exit, exec, wait, create, remove, open, filesize, read, write, seek, tell, close)

Project 5: Virtual Memory

• Creates frame table and supplemental page table to map virtual pages to physical frames
• Implements loading and swapping of executables, stack pages, and mmap files
• Implements stack growth
• Implements page reclamation on process exit
• Implements eviction of pages via clock algorithm

Project 6: File Systems

• Implements buffer cache to replace read/writes directly accessing file system
• Implements read/write locks for file system synchronization
• Replaces extent-based file system with indexing via direct, singly indirect, and doubly indirect blocks
• Implements subdirectories and relevant syscalls (chdir, mkdir, readdir, isdir, inumber)