Display a message on the screen

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                  | CALL  IGMESS (N,CHMESS,CHTIT,CHOPT) |
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Action: This routine allows to display a message. The X11 version of HIGZ displays the message in a separated window. Parameter Description:
N
Number of lines in the message.
CHMESS(N)
Message to be displayed.
CHTIT
Window title.
CHOPT
Options.
'P'
Print the array CHMESS and open the message window if necessary.
'C'
Close the message window.
'T'
Print the array CHMESS on standard output.
'D'
Delete the message window.