Cls

Clears the screen in both text modes and graphics modes

Syntax
   Declare Sub Cls ( ByVal mode As Long = 1 )

Usage
   Cls mode

Parameters
   mode
      A optional numeric variable with a value from 0 to 2.  If omitted, it 
      defaults to 1.

Description
   An optional mode parameter may be given,

      If omitted, Cls clears either the text or graphics viewport.  If a 
      graphics viewport has been defined using the View (Graphics) 
      statement, the graphics viewport is cleared.  Otherwise, the text 
      viewport, defined by View Print, is cleared.  (If there is no 
      explicit text viewport defined, the entire screen is cleared.)

      If 0, clears the entire screen

      If 1, clears the graphics viewport if defined.  Otherwise, clears the 
      text viewport

      If 2, clears the text viewport

Example
   '' set the color to light grey text on a blue background
   Color 7, 1

   '' clear the screen to the background color
   Cls

   '' print text in the center of the screen
   Locate 12, 33
   Print "Hello Universe!"

In graphics modes, if you want to clear the entire screen to color 0, it 
can be faster using  Clear to write zeroes to the screen memory than 
calling Cls.

   Dim scrbuf As Byte Ptr, scrsize As Integer
   Dim As Long scrhei, scrpitch
   Dim As Integer r = 0, dr = 1

   ScreenRes 640, 480, 8

   scrbuf = ScreenPtr: Assert( scrbuf <> 0 )
   ScreenInfo( , scrhei, , , scrpitch )
   scrsize = scrpitch * scrhei

   Do
      
      '' lock the screen (must do this while working directly on screenbuffer)
      ScreenLock
         
         '' clear the screen (could use Cls here):
         Clear *scrbuf, 0, scrsize
         
         '' draw circle
         Circle (320, 240), r
         
      ScreenUnlock
      
      '' grow/shrink circle radius
      r += dr
      If r <= 0 Then dr = 1 Else If r >= 100 Then dr = -1
      
      '' short pause in each frame (prevents hogging the CPU)
      Sleep 1, 1
      
      '' run loop until user presses a key
   Loop Until Len(Inkey) > 0

Differences from QB
   * None

See also
   * Color
   * Locate
   * Print
   * ?
   * View (Graphics)

