SCREEN Statement Syntax Correction for QuickBasic, Basic PDS

This article was previously published under Q78094
This article has been archived. It is offered "as is" and will no longer be updated.
SUMMARY
The correct syntax of the SCREEN statement is
SCREEN [mode][,[colorswitch][,[apage][,vpage]]]
There are two additional restrictions on the SCREEN statement:

  • You cannot specify a comma at the end of the statement without a value following the comma.
  • SCREEN without arguments is invalid and produces an "Illegal
       Function Call" error.						
(Adding these restrictions to the syntax diagram would make thediagram long and difficult to interpret.)

The syntax of the SCREEN statement is incorrect in the following sources,and should be replaced with the above syntax:

  • QB Advisor online Help system in QB.EXE in QuickBasic version 4.5
  • Page 288 of the "Microsoft QuickBasic 4.5: Programming in Basic" for MS-DOS manual
  • Microsoft Advisor online Help system in QBX.EXE in Basic Professional Development System (PDS) versions 7.0 and 7.1 for MS-DOS
  • Page 309 of the "Microsoft Basic 7.0: Language Reference" manual for Basic PDS versions 7.0 and 7.1
MORE INFORMATION
The SCREEN statement syntax is incorrectly documented in QB Advisoronline Help system for QuickBasic 4.5 and the "Microsoft QuickBasic4.5: Programming in Basic" manual as:
SCREEN [mode][,[colorswitch]][,[apage]][,[vpage]]
This syntax incorrectly states that any comma and the followingargument can both be omitted. For example, this syntax is ambiguouswhen you specify three arguments; it is not possible to tell if thesecond argument is "colorswitch" or "apage".

You may omit an argument to the SCREEN statement only whenone of the following conditions holds:

  • The argument omitted is the last argument.
  • You specify a comma following the omitted argument.
The SCREEN statement syntax is incorrectly documented in the MicrosoftAdvisor online Help system in QBX.EXE for Basic ProfessionalDevelopment System (PDS) 7.0 and 7.1 for MS-DOS, and in the manual"Basic Language Reference" for Basic PDS 7.0 and 7.1 as:
SCREEN mode[,[colorswitch][,[apage][,vpage]]]
This syntax incorrectly states that the first argument, "mode" isrequired; it is optional.
QuickBas BasicCom 4.50 7.00 7.10
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Article ID: 78094 - Last Review: 02/27/2014 18:30:39 - Revision: 1.2

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