The Apple Macintosh’s 1.44MB 3.5" disks, Zip disks, CD-ROMs, and hard disks use the same low level format as the PC. As a result, a PC can read and write to these media with a Macintosh format using an application such as MacDrive 98.
The Mac has two other disk formats (400KB and 800KB Mac disk formats) that are usable only on a Mac system. These formats were developed around the time the PC was using 720KB disks. Apple decided that the extra increase of 80KB, more than 10 percent, over the 720KB disks was an advantage.
As it turned out, the extra space was a boon to Mac users, but it isolated the Macs because PCs couldn't read or write these disks. Adding MacDrive 98 won't let a PC read or write the 400KB and 800KB Mac disk formats either. The problem arises because of the way the early Macintosh drives operated.
Although the old Mac 3.5" drives looked comparable to PC 3.5" drives, the two were different underneath. The Mac drive could control the speed of the disk, which let you include the additional data on the disk. The fixed-speed PC drives could never read or write these disks.
Fortunately for Mac users, the Mac drives could read and write the 720KB PC disks, thereby providing a basic exchange mechanism. Although some Macs only have 400KB and 800KB support, all new Macs have the new 1.44MB 3.5" drives.
Older Mac software and data on 800KB disks isn't available to PCs running MacDrive 98. Fortunately, software and data on the newer 1.44MB 3.5" disks and CD-ROMs is accessible.