_gtBox()           Draw a box on the screen
 _gtBoxD()          Draw a double-line box on the screen
 _gtBoxS()          Draw a single-line box on the screen
 _gtColorSelect()   Activate an attribute in current CA-Clipper color setting
 _gtDispBegin()     Begin buffering screen output
 _gtDispCount()     Return the number of pending _gtDispEnd() requests
 _gtDispEnd()       Release the display buffer
 _gtGetColorStr()   Get the CA-Clipper color attributes setting
 _gtGetCursor()     Get the current cursor shape
 _gtGetPos()        Get the cursor location
 _gtIsColor()       Determine if current screen display has color capability
 _gtMaxCol()        Determine the maximum screen column
 _gtMaxRow()        Determine the maximum screen row
 _gtPostExt()       Return control to the General Terminal system
 _gtPreExt()        Prepare the area manager for manipulation of the terminal
 _gtRectSize()      Determine the buffer size needed to save a screen region
 _gtRepChar()       Replicate a character to the screen
 _gtRest()          Display a saved screen region at a specified location
 _gtSave()          Save a screen region for later display
 _gtScrDim()        Get the current screen dimensions
 _gtScroll()        Scroll a region of the screen
 _gtSetBlink()      Toggle asterisk (*) interpretation in color strings
 _gtSetColorStr()   Change the CA-Clipper color attributes setting
 _gtSetCursor()     Set the cursor shape
 _gtSetMode()       Change display mode to specified number of rows & columns
 _gtSetPos()        Move the cursor to a new position
 _gtSetSnowFlag()   Toggle snow suppression
 _gtWrite()         Write a string to the current screen location
 _gtWriteAt()       Write a string at the specified screen location
 _gtWriteCon()      Perform a console style write to the screen