IBM Personal Computer AT Manual To Operations page 105

NUL Null
Used with ESC B and ESC D as a list
terminator. NUL is also used with other
Printer Control Codes to select options (for
example, ESC S).
LPRINT CHR$(O);
SI Shift In (Compressed Character)
Changes the printer to the Compressed
Character print mode.
LPRINT CHR$(15);
SO Shift Out (Double Width One Line)
Changes the printer to the Double Width
print mode.
Note: CR, LF, or DC 4 cancels Double
Width print mode.
LPRINT CHR$(14);
Graphics Printer 1-45