$SY[STEM] contains a string that identifies the executing M instance. The value of $SYSTEM is a string that starts with a unique numeric code that identifies the manufacturer. Codes are assigned by the MDC (MUMPS Development Committee).

$SYSTEM in GT.M starts with "47" followed by a comma and the evaluation of the environment variable gtm_sysid. If the name has no evaluation, the value after the comma is gtm_sysid.

GT.M accepts SET $SYSTEM=expr, where expr appends to the initial value up to the length permitted for an initial value; an empty string removes any current added value.