DEPTH CHARGE
Глубинная бомба
David Ahl, 1973
An 8x8x8 cube of ocean, one submarine somewhere inside it, six salvos. After each miss the machine names directions and nothing else: east or west, north or south, deeper or shallower. There is no map, no grid on the screen, not one picture. You hold the cube in your head or you lose it.
- sectors
- 20-23
- source lines
- 69
- salvos
- 6
Run this disk · The image, 256,256 bytes
Why this one matters
DEPTH CHARGE came through the same 1973 collection as BAGELS, and it was a fixture in school computing rooms for one reason: it is binary search wearing a uniform. The submarine is a number in three parts, the salvo is a probe, and the answer tells you which half of each axis to throw away. Nobody had to explain that. Children worked it out by playing badly for twenty minutes and then playing well. Games like this taught more people about search than any lesson did, because losing six salvos in a row is a better argument than a blackboard.
Three dimensions without a picture
The Iskra-226 is a character terminal. Not one graphics atom shows up anywhere in the corpus I decoded, so a program that wants to be three-dimensional has exactly one honest option, which is to describe. ГЛУБЖЕ and МЕЛЬЧЕ, deeper and shallower, are the third axis, and they work because the player builds the cube. Six salvos against 512 cells sounds cruel until you work it out: a miss reports on all three axes at once, and eight values per axis need three halvings. Three well placed salvos are enough. Six is generous.
What it cost the interpreter
DEPTH does very little by itself. Before it offers the first salvo it calls out six times to two subroutines, one for the generator and one for truncation, and every one of those calls has to come back. A program built that way does not survive a wrong RETURN. The classics pack is where I learned that the token is 0x5E and not 0x2D, which turns out to be LOAD. A decoder can carry a mistake like that for months with nothing looking broken. An assembled program that has to actually run cannot.
What this disk is not
None of this was dug up. The disk was written in 2026, in a dialect I decoded from six recovered sides, using an assembler I wrote for the purpose. The mechanic is common property and has been since the seventies. The Russian code is mine, line by line, and there is no Soviet games disk behind it. I say that on every one of these pages because the alternative is that someone eventually cites an invention as a source, and everything else I have written about this machine goes down with it.
What I checked
DEPTH, a miss at (4,4,4) against target (6,0,5) returns "ВОСТОЧНЕЕ / ЮЖНЕЕ / ГЛУБЖЕ", then the sinking.
What this does not show
The seed is fixed at 37, because no clock or timer atom is attested, so the submarine sits in the same cell on every run and the game is solvable from memory the second time. What is tested is the emulator, not the hardware; the bytes follow the attested rules, and only a test on a surviving Iskra-226 could show whether real firmware accepts them.
Where to read more
- Depth Charge in BASIC Computer Games Dana Noftle's listing, the one that puts a submarine in a cube and then refuses to draw it.
- BASIC Computer Games, the whole book Ahl's 1978 collection scanned end to end, which holds six of the seven titles on my classics disk.
- DEPTH.bas, the source Sixty-nine lines, six calls out to two subroutines before the first salvo, and every one of them has to come back.
- The classics pack The seven titles as one disk, including the RETURN token that this one settled at 0x5E.
The source
DEPTH.bas, 69 lines, assembled onto the image with iskra_asm.py
69 lines of BASIC
10 REM DEPTH CHARGE 20 PRINT "*** ГЛУБИННАЯ БОМБА ***" 30 PRINT "ПОДЛОДКА В КУБЕ 8Х8Х8." 40 PRINT "ВВОДИТЕ X, Y, ГЛУБИНУ." 50 V50 = 37 60 GOSUB 900 61 V61 = V50 / 13 62 GOSUB 950 63 V01 = V60 64 GOSUB 900 65 V61 = V50 / 13 66 GOSUB 950 67 V02 = V60 68 GOSUB 900 69 V61 = V50 / 13 70 GOSUB 950 71 V03 = V60 80 V10 = 0 100 V10 = V10 + 1 110 IF V10 > 6 GOTO 700 120 PRINT "--- ЗАЛП";V10 130 INPUT V04 131 INPUT V05 132 INPUT V06 140 IF V04 = V01 GOTO 150 141 GOTO 200 150 IF V05 = V02 GOTO 160 151 GOTO 200 160 IF V06 = V03 GOTO 600 200 PRINT "МИМО." 210 IF V04 < V01 GOTO 215 211 GOTO 220 215 PRINT "ВОСТОЧНЕЕ" 216 GOTO 230 220 IF V04 > V01 GOTO 225 221 GOTO 230 225 PRINT "ЗАПАДНЕЕ" 230 IF V05 < V02 GOTO 235 231 GOTO 240 235 PRINT "СЕВЕРНЕЕ" 236 GOTO 250 240 IF V05 > V02 GOTO 245 241 GOTO 250 245 PRINT "ЮЖНЕЕ" 250 IF V06 < V03 GOTO 255 251 GOTO 260 255 PRINT "ГЛУБЖЕ" 256 GOTO 100 260 IF V06 > V03 GOTO 265 261 GOTO 100 265 PRINT "МЕЛЬЧЕ" 266 GOTO 100 600 PRINT "*** ПОТОПЛЕНА С";V10;" ЗАЛПА! ***" 610 END 700 PRINT "*** ПОДЛОДКА УШЛА ***" 710 PRINT "ОНА БЫЛА В";V01;V02;V03 720 END 900 V50 = V50 * 21 910 V50 = V50 + 13 920 IF V50 < 100 GOTO 940 930 V50 = V50 - 100 935 GOTO 920 940 RETURN 950 V60 = 0 960 IF V61 < 1 GOTO 990 970 V60 = V60 + 1 980 V61 = V61 - 1 985 GOTO 960 990 RETURN