System 4



System 4 is the fourth major upgrade of the Macintosh system software. System 4 was first released in January 1987.

Features
System 4.0:
 * Was not a major update, but it did have some changes and new features.
 * Introduced AppleShare, a file server.

System 4.1:
 * Made for the release of the Macintosh II and SE.
 * Updated the LaserWriter Driver to 3.3.

System 4.2:
 * About the Macintosh dialog box was improved, now contained RAM usage as seen through Mac OS 9.
 * The Color menu was displayed on color capable Macs.
 * Backgrounder, DA Handler, Early Access, and Print Moniter were added.
 * Cooperative multitasking via MultiFinder was added.
 * Updated the LaserWriter Driver to 4.0.

Versions of System 4

 * System 4.0
 * System 4.1
 * System 4.2
 * System 4.3