This is a port of a classic text-based "lunar lander" game to Fortran.
The first time I saw a computer was when my father took me to an open-house at the IBM headquarters in Atlanta in the late 1970's, when I was around ten years old. I wasn't impressed with the big sterile glass rooms filled with big blue computers, but there was a room in the basement where a couple of bearded guys asked me to sit down at a terminal and play a game.
It was this lunar landing game. For each ten seconds of game time, it asks how much thrust you want to use, and then it tells you your new altitude, velocity, and remaining fuel. I crashed, and then I had to get up to let the next kid take a turn.
It was simple, primitive even, but I was immediately fascinated with computers. I saw that a computer would let me create little simulated universes that followed whatever rules I could imagine.
So after that I kept bugging my dad to buy me books about programming. A couple of years later, my parents bought me a computer. Thanks Mom and Dad!
I did some research, and I found the original Lunar Lander program by Jim Storer, written in the FOCAL programming language in 1969. I've rewritten it in Fortran 95 so that it can be built and run on modern systems. The program here is pretty close to what I remember. One difference is that, on crashing, that program announced "IT'S ALL OVER BUT THE SHOUTING", which confused me as a ten-year-old. I thought the shouting was for joy.
This code is based upon these sources:
- Jim Storer's original lunar landing simulation code in FOCAL
- FOCAL Programming Manual
- David Ahl's port to BASIC in BASIC Computer Games (1978)
- My port to C
If you have a UNIX-ish system with GNU Fortran installed, you should be able to build the executable and play the game by running this command:
make run
The code is intended to be compatible with any Fortran system that supports the Fortran 95 standard. I would like to know of any incompatibilities, and what is necessary to work around them.
Here is an example play session:
CONTROL CALLING LUNAR MODULE. MANUAL CONTROL IS NECESSARY
YOU MAY RESET FUEL RATE K EACH 10 SECS TO 0 OR ANY VALUE
BETWEEN 8 & 200 LBS/SEC. YOU'VE 16000 LBS FUEL. ESTIMATED
FREE FALL IMPACT TIME-120 SECS. CAPSULE WEIGHT-32500 LBS
FIRST RADAR CHECK COMING UP
COMMENCE LANDING PROCEDURE
TIME,SECS ALTITUDE,MILES+FEET VELOCITY,MPH FUEL,LBS FUEL RATE
0 120 0 3600.00 16000.0 K=:0
10 109 5016 3636.00 16000.0 K=:0
20 99 4224 3672.00 16000.0 K=:0
30 89 2904 3708.00 16000.0 K=:0
40 79 1056 3744.00 16000.0 K=:0
50 68 3960 3780.00 16000.0 K=:0
60 58 1056 3816.00 16000.0 K=:0
70 47 2904 3852.00 16000.0 K=:170
80 37 1474 3539.86 14300.0 K=:200
90 27 5247 3140.80 12300.0 K=:200
100 19 4537 2710.41 10300.0 K=:200
110 12 5118 2243.83 8300.0 K=:200
120 7 2285 1734.97 6300.0 K=:200
130 3 1990 1176.06 4300.0 K=:200
140 0 5040 556.96 2300.0 K=:170
150 0 1040 -21.20 600.0 K=:0
160 0 1087 14.80 600.0 K=:0
170 0 606 50.80 600.0 K=:30
180 0 436 -27.90 300.0 K=:0
190 0 581 8.10 300.0 K=:8
200 0 425 13.17 220.0 K=:10
210 0 253 10.30 120.0 K=:9
220 0 95 11.11 30.0 K=:100
FUEL OUT AT 220.30 SECS
ON THE MOON AT 226.11 SECS
IMPACT VELOCITY OF 21.35 M.P.H.
FUEL LEFT: 0.00 LBS
CONGRATULATIONS ON A POOR LANDING
TRY AGAIN?
(ANS. YES OR NO):NO
CONTROL OUT