Monoculture

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Thursday 9 October 2008 @15:50

Insightful Slashdot post of the day, by Haeleth (414428)

This is why the Microsoft monoculture is bad

Back in the ’80s and early ’90s, people coped perfectly well with competing computers and operating systems. Sure, an Amiga was a bit different from an Atari, which was a bit different from a PC, which was a bit different from a Mac, which was a bit different from an Archimedes… but so what? People coped, just like they cope with the way every washing machine or DVD player today has a different interface. When you started using computers, you became computer literate, just like everyone’s more or less washing-machine-literate and DVD-player-literate. And once you’re literate in a technology, you can learn to use any form of it relatively easily.

What the Windows monoculture has done is to destroy computer literacy among most users. Now, instead of learning to use a computer, people are trained to use Microsoft Windows. Instead of learning about launching applications and using word processors, they’re trained to click on the big button at the bottom left of the screen that says “start”, then to click where it says “Microsoft Word”. And so as soon as that button turns into a picture of a foot at the top left of the screen, and the icon they’re looking for says “Word Processor”, they’re left bewildered and uncomfortable.

Of course, this has now bitten Microsoft too: it’s one reason why Vista and Office 2007 are so unpopular.

GeekOS in VGA

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Saturday 20 January 2007 @16:11

The first week of classes seemed to go okay. I’m excited about exchanging code with students using Subversion. Not for group projects, mind you, but in place of downloading my support code and stubs, then emailing back their solutions.

Today I’ve been toying with GeekOS, trying to increase my understanding, and look for other projects to do with it. When I was taking and teaching OS at Maryland, I recall doing much lower-level projects: video and keyboard drivers, getting the task switching code to work, etc. Finally understanding the task switching mechanism was a big eureka moment, I believe. I kept trying to figure out how to jump to the next task in the queue, when really what you do is return to it. From the point of view of each task, it makes a call to the Yield() function, and then sometime later, returns from it. The whole trick is to do the context and stack switch and make the call from one task return to another.

Anyway, GeekOS seems to be designed for higher-level projects now, because the video, keyboard, and task-switching code is all in place from the start. But of course, that doesn’t prevent me from clearing it away, down to just the bootstrap code, and taking my students along on that journey.

Next week, I’m going to talk about PC video modes, and how to write characters and attributes (colors) to video memory. So today I started playing with basic VGA modes, the simplest standard one being 320×200 with 256 colors, also known as mode 13h. I imported some bitmap font code from the Linux console drivers, hacked on the screen.c driver a bit, and now I have GeekOS running in VGA:

That’s a 6×11 font, and seemed to be the best-looking choice with the limited resolution and non-square pixels of mode 13h. But it’s parameterized well enough that I can change a few definitions and employ other fonts stolen from Linux. Here’s a more typical 8×8:

Kind of deliciously chunky, and takes me back to those early days of the PC, when many graphical programs had text that looked about like this. Linux also has a 4×6 font, which is pretty much unreadable, but at least you get 80 columns:

(All of the screen-shots are shown here at 67%, so click through to see the actual size.)

A perverse level of virtualization

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Tuesday 16 January 2007 @18:36

So here I am installing a VNC client on my Powerbook so I can connect to my desktop Linux at work and control a VMware installation running Windows XP. And on that virtual XP? I’m running a GeekOS kernel on Bochs.

Just thought I’d share. Although I’d never personally choose XP for anything, I must admit that it has been convenient to be able to run it in VMware, just so I can see what kind of environment the majority of my students are using, and what problems they may run into. All the software I require for my courses is cross-platform, because I don’t want to be tied to anything. I even can cross-compile GeekOS on my PPC Mac and run it on Bochs there.

I managed to get a virtual XP running on my Linux desktop at work, but so far it doesn’t work at home… and that Linux machine at home is so underpowered at this point, I’m not sure I’d want it on there anyway. So using VNC to connect to it from elsewhere made sense.

More on GeekOS later, but so far hacking it is definitely fun. Learned more about segmentation registers on Intel this week than I ever needed to know.

Submit scripts and version control

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Wednesday 13 December 2006 @22:04

Next semester, I’ll be teaching an intermediate programming course on OOP and design patterns in C++. Additionally, I may do a series of projects based on GeekOS in my operating systems course. (I taught CMSC 412 at UMCP before the advent of GeekOS, but I see in it some influences from the more ad hoc projects we did back then.)

Recently I have been thinking about online tutorial, submission, and assessment systems. Since both of next semester’s courses will involve exchanging a good bit of code, I hit on the idea of using Subversion both to distribute project code to my students, and for them to submit their code for assessment. This has been done before; I found a SIGCSE paper on using CVS for this purpose [Reid & Wilson, 2005].

In the old days (the early 1990s), most CS students did their major programming assignments on a semi-centralized (UNIX) system, and most departments maintained some setuid script for managing submissions. At UMCP, my friend Gabe automated the assessment of assignments to amazing levels, with the help of Perl and shell scripts.

An area that I think is under-explored still is using some kind of automated tutor to help students in a CS0 or CS1 comprehend and practice the very fundamentals of programming: conditionals, loops, arrays, etc. There was a special issue of JERIC recently (Journal on Educational Resources in Computing) on automated assessment, but the aim of many of the articles was to save time and give individualized feedback to classes with 400 students. That seems a little dated now — with CS enrollments down as they are — but I guess it may still occur at a few large schools.

I’m interested in automated assessment not for the time-saving or scalability, so much as for a mechanism that can encourage students to practice on their own time, outside of class, and in addition to assigned work. The system should be able to generate a variety of unique problems to solve, offer hints and help, and assess the student’s progress.

Anyway, I did figure out today how to set up Subversion as a submission tool. It requires the (slightly) more sophisticated access control that you get running it from Apache 2 and the authz module. I set up the top-level of the repository with a public/ folder, and folders for each student: alice/, bob/, carol/, etc. The instructor and TAs should be able to read and write anywhere, but students can read from public and read/write their own folders only. Here’s my authz file that seems to do the right thing:

[cs150s07:/]
league = rw
* = 

[cs150s07:/public]
league = rw
* = r

[cs150s07:/alice]
alice = rw

[cs150s07:/bob]
bob = rw

Then, files provided for the assignments are committed to public/a1/, public/a2/, etc. and copied into the student folders with svn copy.

Two tips from the CVS paper that I think are good ideas: first, when students have problems and seek assistance, insist that they commit what they have to the repository, so you can update and help them out without the awkward emailing of files back and forth. When helping a student through a problem face-to-face, check out a fresh copy, show him how to fix the problem, and then wipe the fresh copy so he still has to fix it again on his own.

Second, if we can encourage students to commit often, we may get a better glimpse of their working habits — such as when they start on assignments — and confront them about problems early on. This buys back a little of the surveillance power we had when everyone did their work on the same machine: you know there’s a problem when johnny hasn’t even logged in and the assignment is due in 5 hours.

As this semester is winding down, I feel the need to debrief myself a bit about how it went. But I’m going to try to hold off on that (at least publicly) until all the grades are in!