Reply to decahedron and zerna:-
Thank you for your replies.
Unfortunately your book is "Beginning Visual C++ 6" by Ivor Horton.
My book is "Ivor Horton's Introduction to Microsoft Visual C++ 6.0 Standard Edition".
Although the two books have the same publisher, the same author and nearly the same title, they are totally different. Your book has 22 chapters and 1224 pages, my book has 6 chapters and 264 pages.
The source code in the two books is also totally different.
Anyway, thank you for your trouble.
Best regards, Gavin Murray