cls - clear the screen


cls [NumExpr]


Cls clears the screen of the userís terminal.  The optional argument NumExpr is unused but may appear for the sake of compatibility.  It determines the proper way of clearing the screen by examining the environment variable TERM and looking up the terminal in the systemís terminal capability database, either /etc/termcap or /usr/lib/terminfo


If cls is unable to determine the terminal type or is unable to access the terminal capability database, it does nothing. 

If the environment variable BASECHO is set to a non-null value when a Basmark QuickBASIC program begins executing, the BASIC input/output facility operates differently in order to support half-duplex terminals such as the IBM 3278.  In this modified behavior of the input/output facility, the terminal modes are not altered.  Cls may fail to work properly under some circumstances because of post-processing by the terminal driver. 

from The Basmark QuickBASIC Programmerís Manual by Lawrence Leinweber