advr.hlp (Topic list)
Important Notice
The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.
CLS Statement Details
  Summary  Details  Example                Contents  Index  Back
──────────────────────────────────────────────────────────────────────────────
 CLS [0 | 1 | 2]
 
 Usage Notes
   ■ If no object is specified, CLS behavior is determined by its location
     in code:
     • If CLS is used in a form module, it is a method, and applies to the
       default form. See: CLS Method
     • If CLS is in a non-form or code module, it is a statement, and applies
       to the entire screen.
 
   ■ If CLS is used as a statement (with the arguments 0, 1, or 2) when forms
     are showing, Visual Basic generates the error message, "Invalid
     when forms are showing."
 
   ■ To use the CLS statement with arguments 0, 1, or 2, you must first
     unload or hide any visible forms.
     See: HIDE Method  UNLOAD Statement
 
   ■ The behavior of a particular CLS statement depends on:
     • The CLS statement argument ( 0, 1, 2, or none).
     • The current screen mode.
     • Whether or not a VIEW statement has been executed that has changed the
       graphics viewport from the default of the entire screen.
     • Whether or not a VIEW PRINT statement has been executed that has
       established a user-defined text viewport.
     • Whether or not a KEY ON statement has been executed that has
       established the bottom text line as a list of function-key
       assignments. The bottom line on the screen may be 25, 30, 43, or 60,
       depending on the current screen mode.
 
   ■ The following conditions determine how the CLS statement works with
     graphics and text viewports:
     • Screen mode 0 has only a text viewport. All other screen modes have
       both a text and graphics viewport.
     • The default graphics viewport is the entire screen.
     • The default text viewport is the entire screen, except for the bottom
       line of text.
     • After a user-defined graphics viewport (or "clipping region") has been
       established by executing a VIEW statement, it is reset to the default
       by executing any of the following statements:
       ■ VIEW without arguments
       ■ CLEAR
       ■ Any SCREEN statement that changes the screen resolution
     See: CLEAR Statement  SCREEN Statement  VIEW Statement
 
     • After a user-defined text viewport has been established by executing
       a VIEW PRINT statement, it is reset to the default by executing any of
       the following statements:
       ■ VIEW PRINT without arguments
       ■ Any text-oriented statement (such as WIDTH) that changes the number
         of text columns or text lines on the screen
     See: VIEW PRINT Statement  WIDTH Statement
 
     • If the KEY ON statement has been executed, CLS statement regenerates
       the bottom screen line as the function-key assignment list or as a
       line of blank characters.
     See: KEY Statement (Assignment)
 
   ■ The following table summarizes how the CLS statement works:
 
     Statement    Condition               Operations Performed
     ═════════    ════════════════════    ══════════════════════════════════
     CLS 0        Any screen mode or      • Clears entire screen of all text
                  combination of user-      and graphics except bottom text
                  defined viewports         line
                                          • Clears graphics viewport
                                          • Regenerates bottom text line
                                          • Returns cursor to home
 
     CLS 1        Graphics screen mode    • Clears default graphics viewport
                  with no user-defined    • Does not clear text viewport
                  graphics viewport       • Regenerates bottom text line
                                          • Returns cursor to home
 
     CLS 1        Graphics screen mode    • Clears user-defined graphics
                  with user-defined         viewport
                  graphics viewport       • Does not clear text viewport
                                          • Does not regenerate bottom text
                                            line
                                          • Does not return cursor to home
 
     CLS 1        In screen mode 0        No effect
                  (text mode)
 
     CLS 2        Any screen mode         • Clears text viewport
                                          • Does not clear graphics viewport
                                          • Does not regenerate bottom text
                                            line
                                          Note: The bottom line of text will
                                          not be cleared even if included in
                                          the user-defined text viewport.
 
      CLS         Graphics-screen mode    • Clears default graphics viewport
                  with no user-defined    • Regenerates bottom text line
                  graphics viewport       • Returns cursor to home
 
      CLS         Graphics-screen mode    • Clears graphics viewport
                  with user-defined       • Does not regenerate bottom text
                  graphics viewport         line
                                          • Does not return cursor to home
 
      CLS         In Screen mode 0        • Clears text viewport
                  (text mode)             • Regenerates bottom text line
                                          • Returns cursor to home