tells Gri to open the indicated file (in
the current directory) as an input data file.  You can specify files
outside the current directory by using conventional unix-shell pathnames
(e.g., `<font color="#82140F"><code>open ~/data/TS/section1/T_S.dat</code></font>' or 
`<font color="82140F"><code>open ../data/file.dat</code></font>').  You can even use "synonyms" (see <a href="Synonyms.html#Synonyms">Synonyms</a>.) in
filenames, as in `<font color="#82140F"><code>open \BASENAME.dat</code></font>'.
<li>
`<fo