Microsoft KB Archive/45169

= PCOPY Causes Screen Snow on Some CGA Video Cards =

Article ID: 45169

Article Last Modified on 11/21/2006



This article was previously published under Q45169



SUMMARY
The program below demonstrates that the PCOPY statement may produce &quot;snow&quot; on some CGA video cards. This is caused by a timing-dependent refresh problem common to many CGA adapters.

This information applies to Microsoft QuickBasic Versions 4.00, 4.00b, and 4.50, to Microsoft Basic Compiler Versions 6.00 and 6.00b for MS-DOS and MS OS/2, and to Microsoft Basic PDS Version 7.00 for MS-DOS and MS OS/2.

The following program is PCOPY.BAS, which uses PCOPY to copy several lines of text to the second page of video memory. When run on a CGA system, screen &quot;snow&quot; will appear during PCOPY. SCREEN 0 PRINT &quot;aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa&quot; PRINT &quot;bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb&quot; PRINT &quot;Watch the snow&quot; PCOPY 0, 1 SCREEN 0,, 1, 1

Additional query words: QuickBas BasicCom

Keywords: KB45169

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