SHOWMESSAGERAPID-Q SpecificWindows/Unix

A statement used to display a generic popup message box.

Syntax: SHOWMESSAGE string-expression
SHOWMESSAGE "Hello world!"

Details
' to get mulitple lines in a ShowMessage box:
CONST CR = CHR$(13)
CONST LF = CHR$(10)
CONST CRLF = CR + LF
SHOWMESSAGE "This will be on" + CRLF + "two lines!"

OR

$ESCAPECHARS ON
SHOWMESSAGE "This will be on\r\ntwo lines!"