1986- Macintosh Plus
The Macintosh Plus was the first real improvement on the Macintosh 128 (The Macintosh 512 was only a Mac 128 with 512 KB RAM).
It had a lot of new features: the extended ROM held the new version of Mac OS, enhanced graphics libraries, drivers for hard-disk and external floppy-disk units, a SCSI bus, AppleTalk networking and the new file manager: HFS (Hierarchical File System).
The new floppy-disk unit could use double-sided 800 KB disks (only one-sided 400 KB for the 128). It had an enhanced keyboard with a numeric keypad and last, but not least, it had a SCSI 1 (1.5 MB/s) interface.
This computer would be succeeded in 1988 by the new Macintosh series: the Macintosh SE and the Macintosh II. However, it stayed in Apple's product line longer than any other Macintosh machine, almost five years, and was on sale until 1990.