This repo was created to collect and share important Operating System concepts from the cs350 course offered at the University of Waterloo 🎓. Feel free to contribute anything else!

• Define Thread
• 5 reasons why use threads?
  • Resource Utilization
  • Parallelism
  • Responsiveness
  • Priority
  • Modularization
• 3 ways to implement concurrent threads
  • Hardware Support
  • Timesharing
  • Hardware + Timesharing
• Define Timesharing
• Define Context Switch
• Define Interrupts
• Define Preemption
• 4 ways to cause context switching
  • Thread_yield (voluntary)
  • Thread_exit (voluntary)
  • Thread blocks following Wchan_sleep() (volunatry)
  • Thread preempted (involuntary)
• 3 thread states
  • Running (on CPU)
  • Blocked (on wait channels)
  • Ready (waiting to run on CPU)
• Know how to draw 2 thread stacks with context switches between them

• Define Critical Sections
• Define Race Conditions
• Define Mutual Exclusion and how to achieve
• Define Test-and-Set and atomic operations
• 4 synchronization primitives
  • Spinlocks
  • Blocking Locks
  • Semaphores
    • Binary Semaphore
    • Counting Semaphore
    • Barrier Semaphore
  • Condition Variables
    • What are mesa-style condition variables? How are they different from Hoare style?
• Deadlocks and techniques for prevention
  • No Hold and Wait
  • Resource Ordering
• Volatile keyword and how it works

• Define Process
• Define Kernel
• Define System Call
• Know how to use basic system calls
  • fork
  • getpid
  • waitpid
  • exit
  • execv
• Define Application Binary Interface (ABI)
• Distinguish between privileged and unprivileged code
• 2 things which make kernel code execute
  • Interrupts
  • Exceptions
• Define Interrupt Handler
• Define Exception Handler
• Distinguish between user (application) and kernel stack
• Know how to draw processes and system calls with details regarding user and kernel stack

• Define physical memory
• Define virtual memory and why we need it
• Memory structure, internal/external fragmentation
• Understand address translation and 3 ways to do it
  • Dynamic relocation
  • Segmentation
    • Relocation Register + Limit register
    • Segment table
  • Paging
    • Single Level paging
    • Multi-Level paging
• Understand the role of MMU in address translation
• Define Translation Lookaside Buffer (TLB)
  • Define software-managed TLB
  • Define hardware-managed TLB
  • Know about what each of the 64 bits in TLB is used for
• Undestand Virtual Memory implementation in OS/161 and its limitations
• Be able to translate virtual addresses to physical addresses using OS/161
• Define Executable Linking Format (ELF) files and their role
  • Understand difference between text segment and data segment in OS/161 ELF files
• Undertand how virtual memory partitioned
  • User addresses from 0x0 to 0x7FFFFFFF
  • Kernel addresses from 0x80000000 to 0xFFFFFFFF
    • kseg0 - 0x80000000 to 0xA0000000 - 512mb - for kernel data structures, stacks, etc
    • kseg1 - 0xA0000000 to 0xC0000000 - 512mb - for addressing devices
    • kseg2 - 0xC0000000 to 0xFFFFFFFF - 512mb - unused
  • Know how to translate kernel virtual addresses to physical addresses
• Define page swapping and how it is implemented
  • Define resident set
  • Define present bit
• Know why page faults happen
• Know about page replacement policies
  • FIFO
  • Optimal
  • LRU
  • Clock Replacement*
• Define locality
  • temporal locality
  • spatial locality

• Define Scheduling and understand why it's needed
  • Define response time
  • Define turnaround time
• Understand different scheduling implementations
  • First come, first serve (FCFC)
  • Round Robin
  • Shortest Job First
  • Shortet Remaining Time First
  • Multi-level Feedback Queue (MLFQ)*
  • Linux Completely Fair Scheduler (CFS)*
• Know 2 different ways of scheduling on Multi-Core processors
• Define Scalabilility
• Define Cache Affinity
• Define Load Balancing

• Define device
• Define bus
  • Define internal bus
  • Define peripheral
• Define bridge
• Define device register and name 3 types
  • Status device register
  • Command device register
  • Data device register
• Define device driver
• Define polling and how to avoid
• Understand how device drivers can access device registers
  • Small data transfer
    • Port-mapped I/O
    • Memory-mapped I/O
  • Large data transfer
    • Program-controlled I/O
    • Direct memory access (DMA)*
• High level understanding of common persistent storage devices
  • Magnetic drums
  • Hard disks
  • SSD
  • Peristant RAM
• Know how to calculate cost of hard disk I/O
  • Calculate seek time
  • Calculate rotational latency
  • Calculate transfer time
  • Request Service time = seek time + rotational latency + transfer time
• Distinguish between sequential and non-sequential I/O
• Understand different disk head scheduling algorithms
  • First come first serve (FCFC)
  • Shortest Seek Time First (SSTF)
  • Elevator Algorithms (SCAN)*
• Basic knowledge of how SSD's work

• Define file
• Define file system
  • Define logical file system
  • Define virtual file system
  • Define physical file system
• Understand basic file operations
  • Open
  • Close
  • Read, write, seek
  • Get, set
• Define directory
• Define i-number and i-node
• Define hard link
• Define mounting
• Understand implementation of Very Simple File System (VSFS)
• Define superblock
• Calculate total space used given file name and inode structure
• Calculate total number of reads and writes on inodes for file operations
• Define chaining
• Define external chaining
• Understand where problems can arise in file operations and how to be fault tolerant
• Define journaling file system

• Define virtual machine
• Define hypervisor
  • Define Type 1 Hypervisor
  • Define Type 2 Hypervisor
• Explain how virtual machine differs from regular machine in terms of
  • Privilege
  • Virtual memory
  • Page tables
  • I/O and devices

1. Pointers
2. LL and SC
3. Context Switch
4. Locks
5. Condition Variable
6. Virtual Memory
7. Disk and Devices
8. File System

1. Threads
2. Synchronization
3. Processes
4. Virtual Memory
5. File Systems

• Recent Midterms - See piazza.
• Past Midterm Exams
• Review Questions Compiled by W10 Students

A big thank you to my Professor Lesley Istead for dedicating her time to teaching this epic course and personally setting all her students up for success. I especially appreciate her initiative and effort to stream her lectures to all students this term.