Q58792: PCOPY Can Fail from Page 0 in 43-Line Mode in SCREEN 0

Article: Q58792
Product(s): See article
Version(s): 7.00
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S900214-56 buglist7.00 fixlist7.10 | mspl13_basic
Last Modified: 6-AUG-1990

In Microsoft BASIC Professional Development System (PDS) version 7.00,
when in 43-line mode in SCREEN mode 0, using a PCOPY statement to copy
screen page 0 to some other screen page may fail. If screen page 0 is
both the visual and active page during the PCOPY statement, it copies
corrupt information to the other screen page. This problem occurs only
in SCREEN mode 0 when in 43-line mode and only when PCOPYing from page
0. It does not occur when PCOPYing from another page to page 0.
Temporarily setting the active and/or visual page to a screen page
other than 0 during the PCOPY corrects the problem.

Microsoft has confirmed this to be a problem in Microsoft BASIC PDS
version 7.00 for MS-DOS. This problem was corrected in BASIC PDS
version 7.10.

The following program demonstrates the problem. A string of 3440 X's
that fills the screen is displayed, then copied from page 0 to page 1.
The visual page is then set to page 1 to view the information copied
from page 0. What appears in page 1 is only a few lines of text,
either at the top or middle of the screen. Setting either the visual
and/or active screen page to any page other than page 0 corrects the
problem.

   WIDTH 80, 43
   PRINT STRING$(3440, "X");
   'SCREEN , ,0, 1    'Uncommenting this line corrects the problem
   PCOPY 0, 1
   LOCATE 10, 10: PRINT " HIT ANY KEY TO SWITCH PAGES "
   SLEEP
   SCREEN , ,0, 1
   END

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