Checkers
This program plays checkers. The pieces played by the computer are marked with an “X”, yours are marked “O”. A move is made by specifying the coordinates of the piece to be moved (X, Y). Home (0,0) is in the bottom left and X specifies distance to the right of home (i.e., column) and Y specifies distance above home (i.e. row). You then specify where you wish to move to.
The original version of the program by Alan Segal was not able to recognize (or permit) a double or triple jump. If you tried one, it was likely that your piece would disappear altogether!
Steve North of Creative Computing rectified this problem and Lawrence Neal contributed modifications to allow the program to tell which player has won the game. The computer does not play a particularly good game but we leave it to you to improve that.
As published in Basic Computer Games (1978):
Downloaded from Vintage Basic at http://www.vintage-basic.net/games.html
The file checkers.annotated.bas contains an indented and annotated
version of the source code. This is no longer valid BASIC code but
should be more readable.
Porting Notes
- If the computer moves a checker to the bottom row, it promotes, but leaves the original checker in place. (See line 1240)
- Human players may move non-kings as if they were kings. (See lines 1590 to 1810)
- Human players are not required to jump if it is possible, and may make a number other illegal moves (jumping their own pieces, jumping empty squares, etc.).
- Curious writing to "I" variable without ever reading it. (See lines 1700 and 1806)