System enabler
System enablers are hardware- specific system additions to the classic Mac OS in order to adapt a certain Macintosh model to an operating system version. It is a single file in the system folder that is loaded at system startup.
System enablers were used to adapt a Mac OS to certain computer models when differences in the hardware required this. The usually only minor changes were incorporated into the next Mac OS version, so that a system enabler for a particular Macintosh was usually only required until the next operating system update .
Apple introduced System Enabler with System 7.1 to adapt the operating system to the multitude of different Macintosh models. These adjustments were integrated into the much more extensive System 7.5 . System enablers were then used to adapt a newly appearing computer model to the current Mac OS. After Mac OS 8.1 , new Macs were shipped with a specially adapted version of the current operating system, so that system enablers were no longer necessary.