ECE421 T, Operating Systems, Spring 2025
Tue & Thurs from 5:05 to 6:20 p.m. in MM 202

The Book

Documentation

Potentially useful source code

Assistance

Assignments

1 due: Thursday 22nd January Five little programs to get used to BCPL.
2 due: Monday 9th February A small library of string functions.
3 due: Friday 3rd April A unified input/output library with basic disc files.

Read the Important Rules link above.
Submit assignments (code + sample run(s)) through blackboard (under Assignments) - THIS SHOULD CHANGE SOON.
Submissions must be clearly readable word documents.
Capture your code as text, not an image: cat, copy, paste.

PC log in - use Putty or your own preferred SSH app. OR mac users: start the terminal app, windows users: start powershell, then type the command
ssh username@rabbit.eng.miami.edu and type your password when prompted.
Windows users beware: you can't use ctrl-V in pico, but page up and page down will do the job.
New advance: windows' terminal app now does an adequate job and is used the same way as the mac version.

Class History

Class 1 - Tue 13-1-2026    A very slight introduction and two motivating mysteries.
Starting BCPL, documentation sections 1 to 13 and 15.
Class 2 - Thur 15-1-2026 Got up to section 38, nearly all done.
Class 3 - Tue 20-1-2026 Extracting and inserting sub-word-length bit sequences,
Frame pointers and how stack frames are organised,
Debugging options and other tricks under our virtual machine.
Class 4 - Thur 22-1-2026 String operations. This link explains what the next four links lead to,
They are two different implementations of the essential parts of the string and "filestring"
objects we had by the end of class, but much tidier than anything I could have written on the board.
strings_one.b, stringstream_one.b, strings_two.b, stringstream_two.b.
Class 5 - Tue 27-1-2026 (look briefly at the tidied strings_two and stringstream_two first)
Taming an unfortunate but common situation: keyboard input, stringstream input.
Design of a trivial and very unhelpful file system.
Class 6 - Thur 29-1-2026 The implementation of file system version 0.
FAT-16, a very bad idea.
Single level index file system, multiple levels of indirection, consequences.
Class 7 - Tue 3-2-2026 SSD needs consideration. Background: C1, C2, C3, C4, C5, C6, C7.
UVEPROMs: X1, X2, X3, X4, X5.
Some SSD details.
Some ancient background to the background: M1, M2, N1.
Class 8 - Thur 5-2-2026 The SSD details that we didn't reach.
NTFS (from Windows NT, 1993) with its runs, inodes (from unix) and fsck etc.
Class 9 - Tue 10-2-2026 ReiserFS.
Disc structure and directories, making very basic files.
Class 10 - Thur 12-2-2026 Review of things fom the quiz, let's hope we learn the lesson.
More with directories, creating and reading files (contiguous allocation),
Here's a little example showing where everything is.
Class 11 - Tue 17-2-2026 The free block list,
how easy it is to change the structure of a file when it gets big,
The fake magnetic tape example extended to copy as well as display.
Class 12 - Thur 19-2-2026 Getting stack frames just right: Program and Memory contents.
Base and Limit for a primitive version of virtual memory.
Just a brief mention of paged and associative memory.
Form your groups of 2 or 3.
Class 13 - Tue 24-2-2026 (unsigned calculations for physical addresses with base and limit)
Interrupts, user and system mode.
Intel's segmentation, a version of base and limit.
Pages and page tables, virtual address translation, 10/10/12, 10/11/11, 9/9/9/9/9/12.
Class 14 - Thur 26-2-2026 A whole VM system (just three processes in the end) all in one picture,
I hope it was clear enough, but it did get a bit crowded, so let me know if anything needs more explanation.
Also most of process creation and life-cycle in unix systems.
Class 15 - Tue 3-3-2026 A neater picture of two processes with virtual memory.
Organising the free page list in four steps: one, two, three, four.
Class 16 - Thur 5-3-2026 Big trouble with shared memory.
Semaphores (one), (two), usually "mutex" these days.
Intel's LOCK, XCHG, BTS, Vax REMQHI, SOBGEQ, Dec-10 SOSL.
The dining philosophers, and anthropomorphic picture of deadlock and solutions.
Break 9th to 13th
Class 17 - Tue 17-3-2026 P and V by software: 0, a, b, c, d, e, f.
Monitors, Java's synchronized.
Some shared single user devices: card punch, card reader, (codes), line printer, graph plotter. How it's done in a program.
Class 18 - Thur 19-3-2026 Review of the essentials for the assignment.
The virtual machine.
Class 19 - Tue 24-3-2026 Complicated virtual address translation tricks to enable modifying page tables.
Class 20 - Thur 26-3-2026 Here's an address calculator to make part of it easier.
All the tricks in pictures.
Doing something real but basic with virtual memory.
That, all put together.
Class 21 - Tue 31-3-2026 Causing a page fault.
Class 22 - Thur 2-4-2026
Class 23 - Tue 7-4-2026
Class 24 - Thur 9-4-2026
Class 25 - Tue 14-4-2026
Class 26 - Thur 16-4-2026
Class 27 - Tue 21-4-2026
Class 28 - Thur 23-4-2026