Screen Control Procedures

 
 The  following  Sections  describe  the procedures available to a user
 program.  These procedures return information about how to  drive  the
 type  of  terminal  currently  in  use.   In the case of phone and PSS
 connections, the TERMINALTYPE command must be used at  some  point  to
 set this up.



VDUI


 %externalintegerfunctionspec vdui(%integer n)

 This  function  returns  various  integer   characteristics   of   the
 terminal. A result of zero is usually an error.

     n = 1   Terminal type
     n = 2   Columns per line
     n = 3   Lines per page (zero for hard copy)
     n = 4   ASCII code for recommended interrupt character
     n = 5   Base character for X position
     n = 6   Base character for Y position


VDUB


 This function returns various boolean characteristics of the terminal.
 A  result  of  zero  indicates  'no'  or  'false',  and  a result of 1
 indicates 'yes' or 'true'.  A result of -1 indicates an error.

 %externalintegerfunctionspec vdub(%integer n)

     n = 1    Home moves cursor to top line
     n = 2    Terminal can operate in page mode
     n = 3    Y coordinate comes first
     n = 4    Terminal auto wraps at line end


VDUC


 This  function  returns  a string which, if sent to the terminal, will
 move the cursor to specified coordinates. A null result indicates that
 the terminal is incapable of controlled cursor positioning.

 %externalstringfunctionspec vduc(%integer x,y)

 The values 'x' and 'y' have an origin of zero (e.g. top left is 0,0).


VDUS


 %externalstringfunctionspec vdus(%integer n)

 This function returns a string.  Sometimes this is a name, but usually
 it  is a value which must be 'printch'd to achieve a particular effect
 on the terminal. A null result indicates that  the  operation  is  not
 supported by that terminal.

     n = 0   Terminal name
     n = 1   Clear screen (cursor moved to home)
     n = 2   Cursor home
     n = 3   Clear to end of line
     n = 4   Clear to end of screen
     n = 5   Initialise terminal
     n = 6   Cursor up
     n = 7   Cursor down
     n = 8   Cursor left
     n = 9   Cursor right
     n = 10  Insert line
     n = 11  Delete line
     n = 12  Set terminal into page mode
     n = 13  Set terminal into roll mode
     n = 14  String to append to start of cursor X movement
     n = 15  String to append to start of cursor Y movement
     n = 16  Two character Unix name for terminal type
     n = 17  Start standout mode
     n = 18  End standout mode
     n = 19  Raw cursor positioning string


PRINTCHS

KEY

 %externalroutinespec printchs(%string(255) s)

 If the length of 's' is > 0, this routine effectively calls  'printch'
 for  each  character  of the string. If the length of 's' is zero, the
 routine has no effect.