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R U B I K ' S C U B E Version 1.03b by Calvin Culver 26 January 1990 I. Introduction.................................2 II. The Opening Screen..........................3 A. The Graphics............................3 B. The Windows.............................3 III. What to Do?................................4 A. The Main Menu...........................4 1. Solving the Cube...................4 2. Playing with the Cube..............5 3. Quitting Rubik's Cube..............5 B. The User Menu...........................5 1. Making Your Move...................5 2. Coloring the Cube..................6 3. Resetting the Cube.................7 4. Saving the Current State...........7 5. Restoring a Saved State............7 IV. Some Final Comments.........................8 V. Disclaimer, Copyright and a Thank You........9 I. Introduction Rubik's Cube began as an extra credit undergraduate project for an introductory Fortran programming course (anybody remember WATFOR?) on a PDP 1170 running the Unix operating system. Ini- tially, it was written for Rubik's Pocket Cube, a 2x2x2 version of the Cube, and was never debugged. The compiler, which appar- ently assembled code in a somewhat linear fashion, could not grab enough memory to compiler the source. My instructor took my problem to her supervisor, who in turn sent me to the department heads, who told me to rewrite the blasted thing in Pascal. For my trouble, I received 5 extra credit points. Well, here I am now, more years later than I want to count, and I finally decided to follow my superiors' advice. Here, completely rewritten in Turbo Pascal, on an IBM XT microcomputer, for a full-size Rubik's Cube, with plenty of memory left over (isn't it amazing how far computers have come in ten years?) is Rubik's Cube. In addition to actually compiling it, I have updat- ed and enhanced the old Fortran version. What started out as just a simple little program to solve the Cube has become a full- blown nightmare (have YOU ever dreamed you were being chased by a ten foot tall cube?) with a full-featured graphics presentation (for Hercules and EGA; CGA just didn't have the resolution I needed), the ability to allow the user to make his own moves, take back moves, reset the cube, or set up the cube any way he likes, and, of course, routines for allowing the computer not only to solve the cube but to save the solution to a text file for later review. And much more. But I'm getting ahead of myself. Actually, the program itself should be straight-forward enough to require little documentation. Those of you who haven't already abandoned me are now dismissed, if you'd like, to get straight on to using the program. I've tried to make the user screens as self-apparent as possible. But, for tidbits, tips and traps, I'd suggest perusing this little tome eventually. II. The Opening Screen A. The Graphics First things first: Do I, you may be wondering, have the proper hardware to run this program, and how do I configure it if I do? No need to worry. Rubik's Cube automatically checks for the proper equipment when you first bring it up. If it can't find anything it likes, it will so inform you and abort; other- wise, it will configure itself automatically for either Hercules or EGA (including VGA) depending on what it sees. (For those of you who have neither Hercules nor EGA, but would like a Rubik's Cube program nonetheless, I do have an older version available, written to use ANSI graphics. It doesn't have all the fancy features of the release version, but if you're interested, con- tact me on my favorite BBS (see below).) B. The Windows When the program first comes up, you will see several things. The left half of the screen is entirely given over to the Cube itself. The first decision I had to make was how to display all six sides of a three dimensional cube on a two dimen- sional screen. This is the method I chose. The Cube window displays two views of the Cube simultaneously: the upper view looks down at the Cube from the front, showing the top, front and right faces; the lower view looks up at the Cube from the back, showing the posterior, bottom and left faces. Both views are updated automatically as moves are accomplished. The right half of the screen is divided between two windows. The upper right quadrant contains the Menu window, wherein the program displays all options currently available. In the lower right you will find the Message window, where Rubik's Cube dia- logues with you, asking you further questions, and informing you of the status of certain things. III. What to Do? A. The Main Menu Initially, the Menu window contains the Main Menu, with two choices available. The first choice is '<A> Computer solves the cube'. The second choice is ' User plays with the cube'. 1. Solving the Cube Selecting <A> causes Rubik's Cube to examine the Cube to see if it is solvable (not every cube state is solvable; for those who are interested, a solved state can only be reached from a small portion of the several quintillion possible combinations of colors. It all involves a lot of higher mathematics. If you'd like to know more, Scientific American had a fascinating article on the Cube back in late 1980 or early 1981, including the mathematics of 'cubology'). If the current state of the Cube is not soluble, Rubik's Cube displays an appropriate message in the Message window and aborts the attempt. Otherwise, you will be prompted as to wheth- er you'd like the steps saved to a text file and, if so, what the name of the file should be. Rubik's Cube then proceeds to solve the Cube. I should pause here to describe the solution file you'll get if you elect to save the solution to disk. This file will have whatever name you decide to give it, with an extension of '.SOL'. The steps in the solution are given in (hopefully) pretty straightforward language, like 'Turn front face clockwise' or 'Turn bottom face half'. The moves themselves are described as if you were looking directly at that particular face of the Cube, and consist of a quarter rotation (90 degrees) of the face in the described direction (or a 180 degree rotation if doing a half turn), but the assignation of the names of the faces depends on your not actually turning the Cube over to look at that face. What I mean by that is this: always keep the top face on top, the right face on the right, and so forth. Otherwise, you'll quite probably get lost very quickly. When you want to execute a counterclockwise turn of the front face, simply turn the front face one quarter turn counterclockwise. On the other hand, a counterclockwise rotation of the posterior face will look, from the front, as if it were turning in the opposite direction (if you were to turn the Cube around so you were look- ing straight at the posterior face you would see that it was, indeed, a counterclockwise rotation). Similarly, a counterclock- wise rotation of the right face will cause that side of the Cube to rotate toward you (assuming you're keeping the front face in the front like you're supposed to be doing), whereas it would take a clockwise rotation of the left face to rotate it toward you. And a clockwise rotation of the top face would rotate it clockwise as if you were looking straight down on the Cube from above, while a clockwise rotation of the bottom face would appear to be clockwise only if you were looking straight up at it from underneath. And it doesn't matter, of course, which way you turn the face when you're doing a half -- or 180 degree -- turn. Was all that too confusing, or are you all smarter than I'm giving you credit for? 2. Playing with the Cube The second choice on the Main Menu is ' User plays with the cube'. Selecting this option opens up to you a whole new world of possibilities, leading straight on into the User Menu which I will describe more fully in the next section. 3. Quitting Rubik's Cube There is actually a third choice available from the Main Menu, as well. To exit the program entirely back to DOS, just press the Escape key (Esc will back you out of any menu to the previous level). B. The User Menu The User Menu itself contains several options, as follows: <A> Make moves Set up the cube yourself <C> Reset cube to original state <D> Save current state <E> Restore a saved state 1. Making your move The first option, 'Make moves', takes you to yet another menu, called the Moves Menu. Here you, the user, can make your own moves, using the arrow keys on your keypad to turn the var- ious faces of the Cube. To turn the left face, for example, just press the left arrow. The up arrow turns the top face, the down arrow the bottom face, Home turns the front face, and End the posterior face. It must be kept in mind that all moves consist of clockwise quarter turns only. Therefore, if you want to rotate a face 180 degrees, you must rotate it two quarter turns. A counterclockwise quarter rotation is accomplished with three clockwise rotations. Thus, for example, to turn the right face one quarter turn counterclockwise, press the right arrow three times. In addition, Rubik's Cube will remember all the previous moves you made, up to 100 moves, allowing you to take back as many moves as you'd like. To take back a move, just press the Delete key. To take back the last four moves you made, press Del four times. 2. Coloring the Cube The second option on the User's Menu is ' Set up the cube yourself'. This option allows you to recolor the cube to your liking, using the available colors. The primary intended use for this option is to allow you to describe to Rubik's Cube the current state of any messed-up Cubes you might have lying around your house. Once you've done that, you can either play with the cube in that state, or, by exiting back to the Main Menu (press Esc once to get back to the User's Menu, then once more to get to the Main Menu) and selecting option A, have the computer solve the Cube (be sure to save the solution to a file so you can use it later to un-mess your Cube). Selecting option will take you to the Set Up Menu. Here you will be shown a list of the colors available to you, and the first part of the top face of the Cube will go black, waiting for you to assign a color to it. You may select a color by typing the first letter of the color (e.g., 'W' for white, or 'G' for green). The current subcube area will be colored according to your selection, and the next subcube will go black to indicate which subcube comes next. You may continue assigning colors in this manner until all subcubes have been defined, or you may press Esc at any time to stop. A caveat to keep in mind here: Once you begin playing with this option you will quickly notice that Rubik's Cube skips over the middle subcube of each face, preventing you from assigning a color to it. Why is that? Well, there is one thing that's true of the middle subcube of every face that's not true of any other subcube: it never moves. Oh, it's true that center subcubes do rotate around, but they never move out of their locations. While the other subcubes wander around all over the Cube, the middle subcubes stay put, so you always know right where to find them. It can easily be seen, therefore, that the color a face is sup- posed to be is determined by what color the middle subcube of that face is. For example, the middle subcube of the computer's Cube's top face is white, therefore, when the computer's Cube is solved, the entire top face will be white. The computer's Cube, when solved, will be white on top, blue on the right, red in front, green on the left, orange in back, and yellow on the bottom. Therefore, before you begin assigning new colors to the computer's Cube, you must first decide what color you own Cube's faces are supposed to be, then pretend they are really the computer's colors. For example, if your Cube's top face is supposed to be blue, when you describe it to the computer you must call it white; i.e. every time you come to a blue subcube on your own Cube, type 'W' instead. 3. Resetting the Cube The next option, '<C> Reset cube to original state', will cause Rubik's Cube to abandon the current state of the Cube and restart it in the original, solved state. This feature is par- ticularly useful, for example, if you've gotten hopelessly lost while playing with the cube and want to just start over, or if you've tried setting up the cube yourself and discovered you've assigned it an insoluble state. In either case, with this option you can wipe the slate clean and start all over again. 4. Saving the Current State Option <D>, 'Save current state' allows you to store the current state of the Cube in a file on disk for later recall. Possible uses here are, for example, if you're right in the middle of solving the Cube and Mother calls you to supper ('Ok, Mom. Be right there!'). Hey, no problem! Just save the current state and go eat dinner. You can then start right where you left off after the dishes are done (yes, I said AFTER the dishes!). Or, if you've just arrived at an especially neat arrangement (like that nifty checkerboard pattern you had a couple of weeks ago) that you don't want to lose, you can save it, too. When you select this option, you will be prompted in the Message window for a file name. You can enter the name (up to eight letters) or just press Return or Esc to abort the save. Rubik's Cube will automatically tack on an extension of '.SAV' when writing the file to disk. First, however, it will check to see if there is already a file on disk by the name and inform you if it finds one. 5. Restoring a Saved State This option is the corollary to the previous one. This allows you to restore a previously saved state. You will be prompted in the Message window for a file name (again, up to eight characters) and Rubik's Cube will automatically assume an extension of '.SAV'. If no file with that name is found, the appropriate message is displayed in the Message window, otherwise the file is read in and the Cube restored accordingly. Again, to return to the previous menu, just press Esc. IV. Some Final Comments Well, that's The Cube. What do you think? It's my sincere wish that you derive oodles and oodles of intense pleasure from it, or at least that it provides occasional relief from the drear of the day. Or, if it gets added to your collection of public domain software never to be looked at again, I guess I can't complain too much. Lord only knows how much PD stuff I have floating around on various disks that I haven't looked at since time immemorial. But I do hope you like it enough to at least trot it out once in a while. Just to let you know in advance, here are some of the en- hancements I have in mind for future editions of Rubik's Cube (that is, assuming I ever get around to putting out future edi- tions): o The ability to record the moves you make in a file on disk, so you go back later and see just how the heck you got to where you are. o Going to a pull-down menu system and/or the use of func tion keys and mouse to select options. o The ability to move around the Cube using arrow keys when setting up the cube. This will be much nicer, for example, if you want to change just one subcube, than having to go through all the previous subcubes to get to it. It will also allow you to go back and correct any mistakes you made without having to start over. o Routines to allow aborting the computer's solving the Cube. It takes, on an 8 mhz XT, about 3 minutes to solve the Cube (I can solve it faster than that myself); currently, once you've chosen that option you're stuck until it's done. This will allow you to abort in the middle. If you have any other comments, good, bad or otherwise (no complaints, though. After all, what have you got to complain about? You get this for free; I'm the one who slaved for months writing it), or any suggestions for improvements or enhancements, you can reach me on my favorite BBS: Computers for Christ #11 (708) 362-7875 Vernon Hills (Chicago), Ill. 1200/2400/9600 PC-Pursuitable Or through the US Mail at: W6999 King Rd. Poynette, Wisc. 53955 (608) 635-2165 V. Disclaimer As per the usual: the author hereby offers no disclaimers as to the suitability or performance of this software on any comput- er, and bears no responsibility for any resulting damage or loss, financial or otherwise. Notice of Copyright This software is owned by me, Calvin Culver, with the exceptions of those portions which are copyrighted by Borland, International. However, I hereby release it to the public domain, and grant anyone the right to freely distribute it as contained herein. My only requirement is that you distribute it "as is" with all files together and intact, INCLUDING ALL DISCLAIMERS AND COPYRIGHT NOTICES, and that you don't try to claim my work as your own (that's called plagiarism, folks, or theft). You may make any modifications you like on your own computer, but please distribute only the original. Regardless of what you may think of my programming skills or the quality of the software, this program is a product of many hours of labor on my part, and I would appreciate it if credit is given where credit is due (in other words, please keep my name associated with it). This copyright notice should in no way be taken to mean that I relinquish any rights with respect to future editions and enhancements of the software, nor does it require me to release such software to the public domain. And finally, it does not allow anyone to make any profit from it without my express writ- ten permission in advance. You may, at your discretion, charge a nominal fee, enough to cover costs of shipping and/or disks if you decide to distribute it in that manner, but you may not sell this program, nor bundle it with other software to be sold, nor use it as an incentive for purchase, without first obtaining my permission. Thank You This release is a token of my gratitude for all the fine public domain software I've been the recipient of over the years. Hmm. Kind of wordy, wasn't it? But I think I've covered everything now. E N J O Y !