Depth Charge
July 5, 2016
Creative Computing was a staple of my programming education; I remember typing in the games to run on a friend’s computer. Here’s a game from the very first issue of the magazine, written by 18-year old Dana Noftle:
In this program, you are the captain of the destroyer, USS Digital. An enemy submarine has been causing trouble and your mission is to destroy it. You may select the size of the “cube” of water you wish to search in. The computer then determines how many depth charges you get to destroy the submarine.
Each depth charge is exploded by you specifying a trio of numbers; the first two are the surface coordinates, the third is the depth. After each depth charge, your sonar observer will tell you where the explosion was relative to the submarine.
Here’s a sample game:
DEPTH CHARGE GAME DIMENSION OF SEARCH AREA? 10 YOU ARE CAPTAIN OF THE DESTROYER USS DIGITAL. AN ENEMY SUB HAS BEEN CAUSING YOU TROUBLE. YOUR MISSION IS TO DESTROY IT. YOU HAVE 4 SHOTS. SPECIFY DEPTH CHARGE EXPLOSION POINT WITH A TRIO OF NUMBERS -- THE FIRST TWO ARE THE SURFACE COORDINATES; THE THIRD IS THE DEPTH. GOOD LUCK ! TRIAL # 1 ? 5,5,5 SONAR REPORTS SHOT WAS SOUTHEAST AND TOO HIGH. TRIAL # 2 ? 3,7,7 SONAR REPORTS SHOT WAS SOUTHEAST AND DEPTH OK. TRIAL # 3 ? 1,9,7 SONAR REPORTS SHOT WAS NORTHEAST AND DEPTH OK. TRIAL # 4 ? 0,8,7 B O O M ! ! YOU FOUND IT IN FOUR TRIES!
The first coordinate is east/west, the second coordinate is north/south. Here is the program that appeared in Creative Computing (pages 18-19):
10 PRINT "DEPTH CHARGE GAME" \ PRINT 20 INPUT "DIMENSION OF SEARCH AREA"; G \ PRINT 30 N = INT(LOG(G)/LOG(2))+1 \ RANDOMIZE 40 PRINT "YOU ARE CAPTAIN OF THE DESTROYER USS DIGITAL." 50 PRINT "AN ENEMY SUB HAS BEEN CAUSING YOU TROUBLE. YOUR" 60 PRINT "MISSION IS TO DESTROY IT. YOU HAVE"N"SHOTS." 70 PRINT "SPECIFY DEPTH CHARGE EXPLOSION POINT WITH A" 80 PRINT "TRIO OF NUMBERS -- THE FIRST TWO ARE THE" 90 PRINT "SURFACE COORDINATES; THE THIRD IS THE DEPTH." 100 PRINT \ PRINT "GOOD LUCK !" \ PRINT 110 A=INT(G*RND) \ B=INT(G*RND) \ C=INT(G*RND) 120 FOR D=1 TO N \ PRINT \ PRINT "TRIAL #"D, \ INPUT X,Y,Z 130 IF ABS(X-A)+ABS(Y-B)+ABS(Z-C)=0 THEN 300 140 GOSUB 500 \ PRINT \ NEXT D 200 PRINT \ PRINT "YOU HAVE BEEN TORPEDOED! ABANDON SHIP!" 210 PRINT "THE SUBMARINE WAS AT"A","B","C" \ GOTO 400 300 PRINT \ PRINT "B O O M ! ! YOU FOUND IT IN "D"TRIES!" 400 PRINT \ PRINT \ INPUT "ANOTHER GAME (Y OR N)", A$ 410 IF A$="Y" THEN 100 42O PRINT "OK. HOPE YOU ENJOYED YOURSELF." \ GOTO 600 500 PRINT "SONAR REPORTS SHOT WAS ", 510 IF Y>B THEN PRINT "NORTH", 520 IF Y<B THEN PRINT "SOUTH", 530 IF X>A THEN PRINT "EAST", 540 IF X<A THEN PRINT "WEST", 550 IF Y<>B OR X<>A THEN PRINT " AND", 560 IF Z>C THEN PRINT " TOO LOW." 570 IF Z<C THEN PRINT " TOO HIGH." 580 IF Z=C THEN PRINT " DEPTH OK." 590 RETURN 600 END
Your task is to rewrite the program in your favored programming language. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.
Programming Praxis 
F# version similar to original:
open System let input() = Int32.Parse(Console.ReadLine()) let rec game() = printfn "DEPTH CHARGE GAME" printfn "DIMENSION OF SEARCH AREA?" let g = input() let n = int ((log (float g)) / (log (float 2))) + 1 printfn "YOU ARE CAPTAIN OF THE DESTROYER USS DIGITAL." printfn "AN ENEMY SUB HAS BEEN CAUSING YOU TROUBLE. YOUR" printfn "MISSION IS TO DESTROY IT. YOU HAVE %d SHOTS." n printfn "SPECIFY DEPTH CHARGE EXPLOSION POINT WITH A" printfn "TRIO OF NUMBERS -- THE FIRST TWO ARE THE" printfn "SURFACE COORDINATES; THE THIRD IS THE DEPTH." printfn "GOOD LUCK !" let rnd = Random() let a, b, c = rnd.Next(1, g + 1), rnd.Next(1, g + 1), rnd.Next(1, g + 1) let report x y z = printf "SONAR REPORTS SHOT WAS " if y > b then printf "NORTH" if y < b then printf "SOUTH" if x > a then printf "EAST" if x < a then printf "WEST" if y <> b || x <> a then printf " AND " if z > c then printfn "TOO LOW." if z < c then printfn "TOO HIGH." if z = c then printfn "DEPTH OK." let another() = printfn "ANOTHER GAME (Y OR N)?" let o = Console.ReadLine().ToUpper() match o with | "Y" -> game() | _ -> printfn "OK. HOPE YOU ENJOYED YOURSELF." exit 0 for i = 1 to n do printfn "TRIAL #%d" i let x, y, z = input(), input(), input() if abs(a - x) = 0 && abs(b - y) = 0 && abs(z - c) = 0 then printfn "B O O M ! ! YOU FOUND IT IN %d TRIES!" i another() else report x y z printfn "YOU HAVE BEEN TORPEDOED! ABANDON SHIP!" printfn "THE SUBMARINE WAS AT %d %d %d" a b c another() game()