Clears the active windows and returns the cursor to the upper-left corner.
Windows, Real, Protected
Sets all character positions to blanks with the currently defined text attributes. Thus, if TextBackground is not black, the entire screen becomes the background color. This also applies to characters cleared by ClrEol, InsLine, and DelLine, and to empty lines created by scrolling.
ClrScr is window-relative. The following program lines define a text window and clear a 60X20 rectangle beginning at (1, 1).
Window(1, 1, 60, 20);