The Plus still did not include provision for an internal hard drive and it would be over nine months before Apple would offer a SCSI drive replacement for the slow Hard Disk 20. For programmers, the fourth Inside Macintosh volume details how to use HFS and the rest of the Mac Plus’s new system software. 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). Macintosh Plus setup with an external floppy drive

Like the 400 KB drive before it, a companion Macintosh 800K External Drive was an available option. 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. The drive was still completely incompatible with PC drives. It has a 3.5″ double-sided 800 KB floppy drive, offering double the capacity from previous Macs, along with backward compatibility. By replacing them with 1MB SIMMs, it was possible to have 4MB of RAM. Four SIMM slots were provided and the computer shipped with four 256K SIMMs, for 1MB total RAM. The Mac Plus was the first Apple computer to utilize upgradable SIMM memory modules instead of single DIP DRAM chips. The Macintosh Plus was the last classic Mac to have a phone cord-like port on the front of the unit for the keyboard, as well as the DE-9 connector for the mouse models released after the Macintosh Plus would use ADB ports. SCSI ports remained standard equipment for all Macs until the introduction of the iMac in 1998. The SCSI implementation of the Plus was engineered shortly before the initial SCSI spec was finalized and, as such, is not 100% SCSI-compliant. The Macintosh Plus was the first Macintosh model to include a SCSI port. Successor: Macintosh SE, Macintosh Classic.

Storage: 3.5″ FDD, double side (800 KB).

How to use a mac plus computer