DOS.MASTER

DOS.MASTER (also known as DOS Master) is a program for Apple II computers which allows Apple DOS 3.3 programs to be placed on a hard disk drive or 3.5-inch floppy disk and run from ProDOS. wrote DOS.MASTER as a commercial program during the late 1980s where it experienced widespread success. It was released into the public domain by his family after the author's death in 2000.

Background
DOS.MASTER was created as a result of Apple Computer's abandonment of the DOS 3.3 operating system and its subsequent replacement by ProDOS. Apple provided a program to copy files from DOS 3.3 volumes to new ProDOS volumes. However, programs written for DOS 3.3 did not run on ProDOS volumes.

DOS.MASTER enabled a widely installed base of previously incompatible DOS 3.3 programs written to be run under ProDOS. DOS.MASTER took a large ProDOS partition, formatted it as a file, and then created a series of DOS 3.3 volumes within that file. The program allowed the user to create one of four DOS 3.3 volume sizes: 140 KB (the standard capacity of an Apple II 5.25-inch floppy disk), 160 KB, 200 KB, or 400 KB (the maximum that DOS 3.3 could address). Up to 255 of these volumes could be created on the larger ProDOS partition (space allowing), effectively simulating a large stack of virtual floppy disk drives.