AC$file extension is for Spooled plot file AutoCAD AutoSpool
Similar to AC$
$00 - DOS Pipe file $1 - ZX Spectrum file in HOBETA format $D$ - Data OS/2 Planner $DB - Temporary file dBASE IV $ED - Editor temporary file MS C $LN - TLink response file Borland C++ $O1 - Pipe file DOS