Programming query Variable DT

["Patricia M. Godfrey" PriscaMG@xxxxxxxx]

Can any Wise Person tell me what the difference is between the Variables
DT and $DT? I observe both in Robert's Table Variables. When I issue
Table Variables , DT displays as 1, $DT as 9. But if I copy
those two lines to a new file, both display as 1. If I then switch to
expanded mode and command VA/NV on the command line, DT comes back as 1,
$DT as 0.
I'm trying to include a routine to check if the file is in expanded
mode, save its value to a SG, switch to draft mode, do something that
cannot be done in expanded mode, then switch back to draft, thus:

XPLeNCODE v2.0
b-gin [UNTITLED]
{<}SX01,{<}VA$DT{>}{>}{<}SX02,0{>}{<}IF{<}VA$DT{>}={<}PV02{>}
{>}[BX_]d DT=1[Q2_]{<}EI{>};*;other code here[cr|lf][BX_]d dt
={<}PV01{>}[Q2_][cr|lf]
-nd
XPLeNCODE

I tried this with both $DT and DT, but I get "command entry error: VADT="
I had originally used 0, but when that bombed tried saving 0 to a SG and
then testing the equation. Still doesn't work. What am I doing wrong?

Patricia M. Godfrey