Lecture 1 - Introduction

Overview

Instructors:

Thanks to them for creating such an amazing course, and making it available to the public! 🫶

7 big principles:

Think about a file list result of the linux command ls -l:

how are files stored on the computer?
if everything is a 0 or a 1 to a computer, there must be some translation and abstraction going on.
there're infinite ways to store files, but the abstraction of a file system is a way to organize them.

Things an operating system designer has to think about to design a file system

How are the files stored? (HHD or SSD), what's the actual low-level form of the file storage.
Important

The files must be located when required.
What's the relationship between a file's name and its data location? <- Hard part to abstraction
Are small files stored diffirently than large files? <- Performance
How are files deleted? Make sure no space going to waste.
Can two filenames point to the same file? To avoid space waste.
Does file data share the same space as file metadata? <- (think: Heap Allocator...)

No matter how those questions are answered, the user should not be able to tell the difference.

Add the -i flag to the ls command to see the inode number of the file.

what the inode is that is associated with that particular path.

Linux and C libraries for file manipulation: stat, struct stat, open, close,read, write, readdir, struct dirent, file descriptors, regular files, directories, soft and hard links, programmatic manipulation of them, implementation of ls, cp, find, and other core Unix utilities you probably never realized were plain old C
programs
Naming, abstraction and layering concepts in systems as a means for managing complexity, blocks, inodes, inode pointer structure, inode as abstraction over blocks, direct blocks, indirect blocks, doubly indirect blocks, design and implementation of a file system
Multiprocessing and Exceptional Control Flow
- Introduction to multiprocessing, fork, waitpid, execvp, process ids, interprocess communication, context switches, user versus kernel mode, system calls and how their calling convention differs from those of normal functions
- Protected address spaces, virtual memory, virtual to physical address mapping, scheduling
  Concurrency versus parallelism, multiple cores versus multiple processors, concurrency issues with multiprocessing, signal masks

The fd abstraction provides direct, low lovel access to stream of data without the fuss of data structures or objects. It certainly can't be slower.
FILE pointers and C++ iostreams work well when you know you're interacting with standard output, standard input, and local files.
- They are less useful when the stream of bytes is associated with a network connection.
- FILE pointers and C++ iostreams assume they can rewind and move the file pointer back and forth freely, but that's not the case with file descriptors associated with network connections.
File descriptors, however, work with read and write and little else used in this course.
C FILE pointers and C++ streams, on the other hand, provide automatic buffering and more elaborate formatting options.