The Mac Plus was the first Apple computer to utilize user-upgradable SIMM memory modules instead of single DIP DRAM chips.

The 800 KB drive has two read/write heads, enabling it to simultaneously use both sides of the floppy disk and thereby double storage capacity.

However, with the increased disk storage capacity combined with 2-4x the available RAM, the external drive was less of a necessity than it had been with the 128K and 512K.

The Mac Plus has 128 KB of ROM on the motherboard, which is double the amount of ROM in previous Macs; the ROMs included software to support SCSI, the then-new 800 KB floppy drive, and the Hierarchical File System (HFS), which uses a true directory structure on disks (as opposed to the earlier MFS, Macintosh File System in which all files were stored in a single directory, with one level of pseudo-folders overlaid on them).

For programmers, the fourth Inside Macintosh volume details how to use HFS and the rest of the Mac Plus's new system software.

A compact Mac, the Plus has a 9-inch (23 cm) 512 × 342 pixel monochrome display with a resolution of 72 PPI, identical to that of previous Macintosh models.

Third-party software applications available included MacDraw, Microsoft Word, Excel, and PowerPoint, as well as Aldus PageMaker.

In January 1988, with reduced RAM prices, Apple began shipping 2- and 4- MB configurations and rebranded it simply as "Macintosh Plus."

On the inside of the case, embossed into it, are the signatures of all the people who worked on designing the Mac Plus, including Steve Jobs, Bill Atkinson, Andy Hertzfeld, Bruce Horn, Jef Raskin and the rest of the historic team.

[9] Due to its popularity, long life and its introduction of many features that would become mainstays of the Macintosh platform for years, the Plus was a common "base model" for many software and hardware products.

As in most early compact Macs, the problem was common in the yoke connector, flyback transformer, and horizontal drive coupling capacitor.

The initial ROM was replaced after the first two months as it had a serious bug which prevented the Mac from booting if an external SCSI device was powered off.