2023-2024 Sem II

This course introduces the design and implementation of operating systems. In particular, we will slowly build the xv6 OS from scratch. Students should feel comfortable with hacking through an OS after having done this course.

Course Information

  • Prerequisites: COL106 and COP290.

    Note: The course includes programming assignments and thus expects proficiency with systems programming and debugging.

  • Credits: 3-0-4
  • Slot: K, Tuesday 5-6pm, Wednesday 12-1pm, Friday 5-6pm
  • Lecture hall: LH111
  • TAs:
    • Abhisek Panda: csz202445 AT cse.iitd.ac.in
    • Rohith Vishnumolakala: csy227589 AT cse.iitd.ac.in
    • Satyam Jay: anz238224 AT iitd.ac.in
    • Saurabh Verma: cs5190129 AT cse.iitd.ac.in
    • Ritesh Srivastava: jcs222656 AT csia.iitd.ac.in
    • Yashashwee Chakrabarty: mcs222057 AT cse.iitd.ac.in
    • Prateek Bhaisora: jcs232564 AT csia.iitd.ac.in
  • Reading material:

Grading criteria

  • 30% labs (programming assignments)
  • 20% project
  • 10% quizzes
  • 20% minor exam
  • 20% major exam
  • 5% errata participation (bonus, optional)


  • Lab 1: mouse driver, disk scheduling
  • Lab 2: crash consistency


  • Ethics: Please re-read IITD honour code. Cheating will get an F in the course. Why should I not cheat?
  • Late policy: To help you cope with unexpected emergencies, you can hand in your labs solutions late. The total amount of lateness summed over all the lab deadlines must not exceed 72 hours. You can divide up your 72 hours among the labs however you like; you don’t have to ask or tell us. You can only use late hours for labs. There will be no makeup labs and no late time extensions.
  • Quizzes: Quizzes will be surprise. There will be no make up quizzes. We will count the scores from your best (n-1) quizzes where n is the total number of quizzes.
  • Audit criteria: 60% or more marks in total. 60% or more marks in major+minor exams. Attempted 75% of quizzes.
  • Errata participation: You can send pull requests to remove dead code, fix bugs and other grammatical mistakes, to receive upto 5% of bonus marks. These marks can only be used to improve grades D and above i.e, they cannot be used to move from grade F to grade D and they cannot be used to move from grade NF to NP.
  • Discussions should be done exclusively on Piazza. Please don’t send individual mails.
  • Makeup minor exam: For those who miss the minor exam, we will hold an extra minor towards the end of the course. Reminor will be much harder than the original minor exam.
  • Fill this sheet if you want to add the course.

Tentative topics

We will build an OS from scratch. We will learn topics as and when we add them to our OS. The topics will tentatively be covered in the following order:

  • Booting: Bootloader, ELF format
  • Input-output: Programmable interrupt controllers, traps, interrupt descriptor table
  • File system: FS layout, buffer cache layer, name layer, crash consistency, devices as files
  • Processes: memory segmentation, rings, process table, context switching, scheduling, system calls, exec system call
  • Concurrency: data races, different types of locks
  • Memory virtualization: memory hierarchy, address translation mechanism, demand paging, page replacement, thrashing, fork system call
  • Shell
  • Parallelism

Whenever we implement something, we will also study some alternate implementations. Following topics will be covered without seeing their implementations.

  • Beyond OS: virtualization, shadow paging
  • Glimpse into OS research: power management, unikernels, persistent memory, transparent huge pages, disaggregated OS

Disclaimer: Actual course contents may differ.


Week Tuesday Wednesday Friday Other
1 2 Jan
LEC 1: Introduction.
Resource management, high-level services.
3 Jan
LEC 2: Introduction.
Protection and isolation, why study it?
5 Jan
LEC 3: x86 ISA.
general registers, eip, eflags, assembly.
2 9 Jan
LEC 4: x86 ISA.
esp, ebp, gcc calling convention, objdump.
10 Jan
LEC 5: x86 ISA.
PIO, MMIO, volatile keyword.
12 Jan
LEC 6: Booting.
BIOS, bootloader, 16-bit mode, segments. Quiz 1.
3 16 Jan
LEC 7: Booting.
ELF file format, segmented and flat memory models.
17 Jan
LEC 8: Booting.
Code walkthrough.
19 Jan
LEC 9: IO.
Polling, interrupts, DMA, PICs, IDT.
20 Jan
LEC 10: IO.
Interrupt handling code walkthrough. Quiz 2. Lab 1 out.
4 23 Jan
LEC 11: IO.
HDDs, disk scheduling.
24 Jan
LEC 12: IO.
RAID, buffer cache code walkthrough.
26 Jan
Republic day
5 30 Jan
LEC 13: FS.
Abstractions, FAT filesystem
31 Jan
LEC 14: FS. Indexed filesystem. xv6 code walkthrough. Quiz 3.
2 Feb
LEC 15: FS. Optimizations, crash consistency via ordering.
3 Feb
Lab 1 due. Lab 2 out.
6 6 Feb
LEC 16: FS.
fsck. Write-ahead logging.
7 Feb
LEC 17: FS.
Metadata journaling, xv6 code walkthrough. Quiz 4.
9 Feb
LEC 18: Cancelled. LEC19 and LEC21 will be 1.5 hr each.
7 13 Feb
LEC 19: Processes.
Address space: heap, stack. Memory APIs and bugs.
14 Feb
LEC 20: Processes.
Memory allocator, free list
16 Feb
LEC 21: Processes.
Slab, buddy allocators. Memory isolation. Protection levels. Quiz 5
17 Feb
Lab 2 due.
8 20 Feb
21 Feb
23 Feb
24 Feb
Lab 3 out.
9 27 Feb
Minor exam
28 Feb
Minor exam
1 Mar
Mid-term project evaluation
4 Mar
Moved to 9 Mar 6:30-7:30pm.
10 5 Mar
LEC 22:
6 Mar
LEC 23:
8 Mar
Maha Shivratri
9 Mar
LEC 24:
Lab 3 due.
11 12 Mar
LEC 25:
13 Mar
LEC 26:
15 Mar
LEC 27:
12 19 Mar
LEC 28:
20 Mar
LEC 29:
22 Mar
LEC 30:
13 26 Mar
Semester break
27 Mar
Semester break
29 Mar
Good Friday
14 2 Apr
LEC 31:
3 Apr
LEC 32:
5 Apr
LEC 33:
15 9 Apr
LEC 34:
10 Apr
LEC 35:
12 Apr
LEC 36:
13 Apr
LEC 37:
16 16 Apr
LEC 38:
17 Apr
Ram Navami
19 Apr
LEC 39:
20 Apr
LEC 40:
17 23 Apr
LEC 41:
24 Apr
LEC 42: