Operating Systems Index

cs111.stanford.edu

Topics

CS111 leverages CS107 experience to show operating systems and how they function.

What is an operating system

• operating system sits between hardware and user programs
• most importantly: manages shared resources to allow the program to run
  • CPU: gets which program to do work and for how long
  • RAM: how much memory to give to a program
  • Hard Drive

Main Events

• concurrency: switch between processes so quickly to only use on core while concurrent access
• memory: memory addresses are mostly scattered everywhere — everything include the lowest level including CPU uses only virtual memory, translated by the OS
• file management
• i/o devices
• networking: CS144
• security: interactions between users in a system

Main Components of the Course

• File Systems
• Process and Multiprocess
• Threads
• Virtual Memory + Paging + limits
• Modern Technologies/Niceties

What’s Next

SU-CS111 Outline

Content

filesystem

How can we design file systems to manage files on disk, and what are the tradeoffs inherent in designing them. How can we interact with the filesystem?

• filesystem
  • Unix V6 Filesystem
    • Freelist and Block Cache
• disk
• crash recovery
  • fsck
  • ordered writes
  • journaling: write-ahead logging
• syscalls
  • kernel mode
  • files handling
    • file
    • file descriptor

multiprocessing

How are programs run, how to spawn subprograms, and how they work in general?

• multiprocessing
• fork
  • execvp
  • waitpid
• shell
• pipe and ipc

Multithreading

How do we implement a single program within a single program, and how do we not have race conditions

• multithreading
  • processes vs threads
  • race condition and mutex
  • passing by reference
• permits model
  • busy waiting
  • condition variable
• Unique Lock

trust

how do we trust software?

• trust by assumption
• trust by inference
• trust by substitution

patterns

• monitor pattern

dispatches

• assembly review
  • process control block
• dispatching
  • trap
  • interrupts
  • context switch
• scheduling
• preemption

virtual memory

“how can one set of memory be shared across several processes”

• virtual memory
  • dynamic address translation
• demand paging
  • clock algorithm

model technologies

• modern OS

trust and OS

• trust

An example of a good time:

void main() {
    // make pipe
    int fds[2];
    pipe(fds);

    pid_t pidp = fork();

    if (pidp == 0) {
        close(pidp[1]);
        dup2(pidp[0], STDIN_FILENO);
        close(pidp[0]);
        execvp("", ...);
        // throw-a-tantrum
        exit(1);
    }

    close(pidp[0]);

    return pidp[1];
}