 The magazine of the Melbourne PC User Group Two QBASIC Programs, Now With More Features Keith Phillips |
Two QBASIC programs, QBchess!.bas and QBfigure.bas,
are available for download from PC Update Online in a file named QB&more!.zip [158 KB]. They
are enhanced versions of programs that have been published in PC Update.
The QBchess!.bas Program
The simple chess program in PC Update November 2000 used QBASIC Screen0, which is a
text-only screen, so letters were used to represent the chess pieces. The program on PC Update
Online uses QBASIC Screen8 which can display both graphics and text. The chess pieces are displayed
as shapes and the prompts are displayed as text. In VGA, Screen8 has four pages of video memory,
each of which can store a screen image. All four video pages can be displayed, but only one at a
time. QBchess!.bas is designed to display chess puzzles, end games and example games and to store
them in data files. Full details are with the program on PC Update Online.
Chess Startup
When the program starts, all the chess pieces are displayed on the board as shown in screen Image
1. Drag and drop moves the chess pieces. A left mouse click on any chess piece marks all the
squares threatened by the piece as shown for a black queen and a white bishop in screen Image 2.
[ Note: These images are contained in the file Image.zip contained
in the main QB&more!.zip file.] The marks are useful for inexperienced chess
players. It is also helpful to drag the piece along a path of marked squares when moving it across
the chess board. A left click on any blank square, or moving a piece, removes all the
marks.
Chess Puzzles to be Solved in Two or Three Moves
Double Left click on "BlankScreen" clears the chess board. Single Left and Right clicks set up the
puzzle. Double Left Click on "CopyMoves" copies the puzzle into one of the pages of video memory.
After each move, Double Left Click on "CopyMoves" copies the move into a different page of video
memory. Finally, Double Left Click on "ViewMoves0123" redisplays the video memory page by
page.
Chess Data Files
There are some example chess data files with the program in QB&more!.zip on PC Update Online.
You can use existing data files and create new data files.
Double Left Click on "SaveF" saves the displayed screen onto the end of a data file. Repeated use
of "SaveF" builds a record of up to 255 moves.
Double Left Click on "LoadF" displays chess moves from data files and it can also edit or delete
data files. When "LoadF" is running the threatened squares can be marked either selectively or
automatically, as shown in screen Image 3. The white marks show all the squares threatened by the
white pieces and the shadow image of the black king shows which square it was moved from. The
shadow piece disappears when any key is pressed.
The QBfigure.bas Program
"Figure It Out" puzzles are published in "The Saturday Age Extra". About three quarters of these
puzzles can be solved by algebra alone. The puzzle in PC Update July 1999 is an example of
this type of puzzle and screen Image 4 shows how QBfigure.bas displays the puzzle at the
stage when all ten letters have been solved.
The puzzle in PC Update August 1999 is an example of a puzzle that can't be completely solved by
algebra. Screen Image5 shows how QBfigure.bas displays the puzzle at the stage when the
table of results appears. The column of white letters shows the values for all the letters,
including the lost letter.
The puzzle in "The Age", 15 April, 2000 is the only example I've seen where there are two possible
values for the missing letter. Screen Image6 shows the puzzle at the stage where H can be either 4
or 6. There are two sets of valid values for the ten equations. However, there is only one valid
result for the missing letter. For H=4 & B=6 the missing letter is C=9, but for H=6 & B=4
the result is ?=11 which is not a valid value.
How to Run These Qbasic Programs
If you don't have copies of qbasic.exe and qbasic.hlp on your hard drive, make a new folder on the
hard drive named C:\QB (Or any other name of your own choice). Click the Start Menu and click Find
to search your Windows 95 or 98 CDRom for qbasic. Copy the two qbasic files into C:\QB (Or your
chosen folder name). Download QB&more!.zip from PC Update Online and unzip it into C:\QB (Or
your chosen folder name) to obtain File_id.diz, Info.zip, QBchess!.zip and QBfigure.zip. Unzip
Info.zip for more information.
FOOTNOTE
QBfigure.bas solves the "Figure It Out" puzzle in "The Age", 24/Feb/01 as: A=8, B=3, C=4,
D=8, E=4, F=7, G=0, H=6, J=2, K=3, which is an unacceptable result because of duplicate values.
Change H=6 in the puzzle to H=9 and the solution becomes: A=5, B=3, C=1, D=8, E=4, F=7, G=0, H=9,
J=2, K=6, which is the published result in "The Age", 3/Mar/01.
Reprinted from the May 2001 issue of PC Update,
the magazine of Melbourne PC User Group, Australia
