15.58.17  SYMBOL 

SYMBOL=sym specifies the symbol to use for plotting data.  Any legal UGSYS
symbol may be used.  Points that do not already have a symbol are normally
plotted using the default symbol (See:Command SET SYMBOL).  The symbol you
specify is used instead of the default.  You  may  change  the  color  and
intensity of a symbol, but it may not have a changed texture.  You can not
plot symbols dotted or dashed.

NOSYMBOL specifies that all points are plotted with the default symbol, or
the selected SYMBOL instead of the symbol assigned to each point.

If  you  want a centered symbol use 0o, 1o, 2o, 3o, 4o, 5o, 6o, 7o, 8o, or
9o.  Some characters from the  ASCII  character  set  are  also  suitable.
"08OXNSYZ$*" are all possible characters which are centered and reasonably
symmetrical.  Lower case characters are too far below the  center  of  the
point.