HW1: Boot Blocks

CS 321 Homework, Dr. Lawlor, 2006/01/20. Due Monday, Jan 30.

Here's a series of problems regarding the x86 "boot block" or "boot sector". You're expected to turn in the result of each problem to Blackboard, by clicking on "Assignments", "View/Complete Assignment", attaching your files, and clicking "Submit" (be careful! "Save" isn't the same as "Submit"!).

Download all the input files for this assignment: (Directory, Zip, Tar-gzip)

Download the x86 PC boot block problem1.bin and run it. You can do this on a real PC by copying the boot block to a floppy disk (in UNIX, just do "dd if=problem1.bin of=/dev/fd0"). But I recommend using the QEMU emulator, where you'd just run "qemu problem1.bin". This boot block will print out four characters and then stop. Turn in the four characters in a text file named "problem1.txt". (Yes, this problem sounds really easy--you've just got to run an existing boot block! But you've got to get QEMU running, and figure out how to use it--that's worth a few points.)
- Friday update: QEMU is annoying to run directly on Windows-- it's not in your PATH, so you've got to pass the absolute path to the executable, *and* it can't find the PC BIOS image, so you have to pass "-L" and the path to the bios/ subdirectory. I've written a little Windows-specific qemu.bat file that directly calls QEMU with the proper arguments. You can drag-and-drop an image like problem1.bin onto qemu.bat, and it should run. Be aware the script assumes you've installed QEMU in the standard "C:/Program Files/qemu", so you'll have to tweak the script if you've installed it elsewhere. This is my bad--I should have tested out QEMU on Windows more thoroughly.
Download the x86 assembly source file problem2.s and the assembler NASM. Compile the source file into a boot block with "nasm -f bin problem2.s -o problem2.bin". Run it like before. Initially, this source file will print out the four characters "Nope". Change the source file so it prints out the same four characters as problem 1, and turn in your modified "problem2.s".
Download the x86 assembly source file problem3.s and run as usual. Change the source file so it continuously echos the characters you type in (alphanumeric only; don't worry about special characters). Also make the 'r' key reboot the machine--but note that QEMU reboots so fast you might not even see it! Turn in your modified "problem3.s".

Reference material:

A good survey of BIOS functions for UNESCO from a university in Vietnam.
Ralph Brown's Interrupt List is the definitive reference for all interrupt functions. See just the BIOS interrupts, like the TELETYPE output interrupt, as other interrupts (like DOS interrupts) aren't available at boot time. We'll have a lecture exclusively on software interrupts, so don't get too worried if they don't really make sense quite yet.
If you haven't written x86 assembly, read my NASM x86 cheat sheet or the NASM Docs.

Open-Ended Problems

Half your homework grade is to complete any five open-ended problems (miniprojects) throughout the semester. I'll try to offer at least one open-ended problem with each week's homework. If you complete more than five open-ended problems through the semester, I'll take the five with the highest grades.

Turn in open-ended problems by naming the source code "problem.s" and submitting it on blackboard as HW1_O. HW1_O is due Monday, February 6 at 5pm.

Write any reasonably interesting interactive game in the boot block. (e.g., character-based pong, brickles, maze, or a 2-person tank battle). Reasonably interesting means it runs and responds to input, not that you could sell it for $39.95.
In the boot block, change the screen to VGA graphics mode and display something reasonably interesting. Heck, a gradient fill is reasonably interesting. Random garbage or a black screen is not interesting.