Manor (1986) - This is probably my magnum opus of BASIC programs. It's a land-management game, inspired by Dukedom but supposed to be much more historically accurate. Looking back on it I realize I got some things wrong and should have done some more serious research on medieval England--but all things considered, I think I did fairly well. You play the role of an earl in 14th-century England, surrounded by fiefs of varying power. Each of your neighbors holds a different rank of nobility, with corresponding size and power: the baron is the smallest and weakest, the viscount's less so, the earl is about your strength, the marquis is stronger, and the duke is biggest and baddest of them all. The game has a rating system that I never did succeed in tweaking to my satisfaction--but it does work, and one of the things I really liked was that you get more points for taking land from a stronger rival. Also keep in mind that when you take land from an opponent, it makes them a bit more likely to take up arms against you in the future (in proportion to the amount of land taken). Likewise when someone's taken land from you, they're more tempted to come back later for seconds. Oh, and you will eventually die of old age, so no immortality in this game.
I should offer some pointers on playing the game. At 12 acres/person, a group (Peasants, Serfs, Nobles) achieves some real self-sufficiency. They can plant plenty of grain for themselves, and leave enough fallow for their land to improve slowly. Too little land (under 8/person or so, I think) and in an effort to feed their families, they will leave too little fallow, and the land's fertility deteriorates. Unfortunately you can't always achieve this throughout your manor without conquest or massive population depletion, and if you do manage it, your population tends to increase due to the availability of food, so ample land is a temporary thing. If you can gather at least 100 or so acres in your demesne (personal estate), you can support yourself without taxing your Peasants or Nobles at all, which makes them happy and improves their health, all things being equal. (This is one of the few areas where the game isn't very well balanced; I probably should have corrected this oversight.) If you get a message saying that a group is malnourished but you aren't offered the chance to feed them (and you have grain available), that means the malnourishment is minimal. If either the Peasants or Serfs decide to rise up against you, the other group will rise up as well, even if it's quite happy. The Nobles will band together to protect you, though, unless they're very upset with you. When you're about to go to war, if the Nobles complain there aren't enough Peasants, they will fight less well (this makes it less effective to just knight all your Peasants). If you're invaded, you're asked whether to retreat to the castle. Holing up in the castle improves the chances of winning, but reduces the amount of your opponent's land you can take if you win. Also, should you incur debts, you will pay interest on them.
One issue you're likely to run into if you play for a while is that the game seems to hang sometimes right after a war. It probably hasn't, in fact. Following a war, the game updates the map to reflect the change in land ownership (X conquered N acres from Y). It uses, I think, a fairly inefficient method--selecting a square at random, checking to see if that square is on the border between the two manors, and if so, changing its ownership. This was a simple way to ensure that it would work anywhere on the map, even if the borders got pretty distorted, and it avoided making changes starting from the top right or some other recognizable pattern. The trouble is that it can sometimes take a while to find a square that's along the border.  It also happens in rare cases that two formerly neighboring manors have lost their common border, so it won't be able to find qualifying squares in any case. Similarly, there's a rare bug that I never did track down, where one manor will attack another that it never has bordered: the Baron (on the left) attacking the Earl (on the right), for instance. To make sure the game does move on at some point, I added a timer that will eventually make it stop looking for squares and proceed with the game; it times out after a minute or two, I think. (Unfortunately I think there are also some rare instances where this part of the game really does hang, but I've never been able to verify it.)
(1984) - An old-style text Star Trek game: destroy all the Klingons before they take over the Federation. This game was heavily influenced by Video Trek 88, Super Star Trek, Apple Trek, and--especially for things like the menu options--Seabattle, oddly enough. When asked for number of Starbases and Klingons, hit Enter for a random number. Coordinates in the game are given as y,x rather than x,y (a misunderstanding on my part when I first wrote the game--when I realized I had them backward, it would have been a real pain to correct it). Your Warp and Impulse engines can each be used to travel either within or between quadrants--it's just that Warp is awkward within quadrants, and Impulse is very slow between them. Higher speeds use more power but take less time. Higher shield strengths give you better protection but consume much more power. Also, the Klingons are somewhat more powerful than they tended to be in other text-based Trek games; in particular, they also fire torpedoes (something Quadrant shares with Apple Trek).
- Struggle for the Continent (1991) - A Risk-like game for 2 or more players. This is meant to simulate World War I, more or less. Different countries' armies have different combat strengths; the strongest are German and Swiss, the weakest Russian. Also, each country has a maximum number of troops that it can mobilize--once you've reached your max, you'd better hope your opponent is almost out or that your allies still have some left. Of course, there's always the possibility of drawing neutrals into the war. The map is based on the 1914 borders, and on the battle lines that were drawn as troops advanced and retreated. Unfortunately the graphics available in GWBASIC are crude, so the map can be very difficult to make out. To help with that, I've included a scanned copy of the map I used when I originally designed this as a board game. Also, the directions that the arrow keys move you don't always seem to make sense: there were times when, say, there were four places you could go to the north, and there are only three keys at the top of the keypad, so I had to make do. So you may find there are times when pushing the right arrow actually moves you northeast, and so forth.
An Aspect of Statistics (ca. 1987-88) - I took a semester of statistics in college--the only math class I've actively enjoyed, largely because it felt like something I could really use. And indeed I did: I used it to write this program. You input binomial data (x,y) and it will tell you the mean, median, standard deviation, the formula for the best-fitting line, and will even draw a crude scatter diagram showing the best-fitting line. For those not familiar with statistics, the best-fitting line gives you some predictive power; assuming your data forms something like a line, you can use this equation to get an idea what to expect y to be, given x. For instance, you could chart gas prices over time and use the best-fitting line to estimate what the price will be a year from now. In grad school, one of my more self-absorbed professors (not to mention any names) wrote in his comments on one of my papers, "Learn some statistics!"--which was ironic, considering the scatter diagrams in my paper had been generated by this statistics program I wrote. Harrumph.
- Flashcards (1991) - As the name suggests, a program that does flash cards. It lets you enter questions and answers, and save them to disk, then use the program to quiz yourself. This helped get me through some of my college finals.
Trek (mid-1980s) - An adaptation of FASA's Star Trek III Starship Combat Role Playing Game, but done on a square instead of a hex grid. This is a turn-based ship-to-ship combat sim. FASA's system allows any number of ships to interact, though to make it (much) simpler to program, my implementation is limited to one-on-one combat. Every three turns you allocate your available power to movement, weapons, and shields (Press * to set a shield to full power). Different ships have more or less efficient shields and movement ratios, more or less accurate beam weapons, and more or less accurate and powerful torpedoes. You can fly Federation, Klingon, Romulan, Gorn, Orion, and even Tholian ships. You can also input your own vessel. This was a big hit on my dorm floor in 1988, 'till the guys found better games to play--like Macintosh Risk.
The Tholian ship was my invention; I created it based on what little was known about Tholians back then. I originally called its beam weapon the "Easer", which was supposed to mean an energy beam comparable to phasers, but I should have thought of a less dopey name for it. In April 2009, I stumbled on an unofficial (but apparently well-developed) site, Star Trek Starship Tactical Combat Simulator, dedicated to maintaining and expanding the old FASA game. I see the folks there have given the Tholians' beam weapon a name: Phaser. Unexciting, I suppose, but that's as close to official as I've seen anywhere on the Web, so I've updated this game to reflect the new name.
Incidentally, if you're interested in seeing how the original form of this game works, I've digitized my copy of the original manual.
Here's a downloadable copy.
Farkle (1997) - This is an implentation of an old dice game that we used to play with my grandfather, Olley Cote, at least as far back as the 1970s. (It's apparently an old folk game which has since been marketed commercially.) This was a family favorite for years, then after his death people stopped playing it, and I later had to reconstruct the rules from memory. Here are the basics: you roll six dice and look for ones that are worth points. A 1 is worth 100; a 5 is worth 50; a combination of three is worth a hundred times the number: so three fours are worth 400 points, etc. Three ones, however, are worth 1000, and a roll of 12345 is worth 1500 points. You set aside the dice you want to keep and can roll again to collect more points--of course, if at any time your roll isn't worth anything, you've "farkled" and get nothing. Also, you have to pull out at least one die per roll, so you can never roll more than five times per turn. The goal is to be the first to reach 5000 points, and you need 500 points in one hand in order to get on the board. Until you get on the board, your scores don't count; so even if you roll 450, you get nothing for that turn if you're not on the board yet. I've always felt that was excessive--when I'm playing the game in real life I tend to ignore the requirement to get on the board. Unfortunately though, I didn't write that option into the game and now it's more trouble than it's worth to go back and add it.