On 10 April 1978 Apple signed a $13,000 contract with Shepardson Microsystems to write a DOS and deliver it within 35 days.

MASTER CREATE includes a self-relocating version of DOS that boots on Apples with any memory configuration.

New firmware included an auto-start feature which automatically found a disk controller and booted from it when the system was powered up—earning it the name "Autostart ROM".

It improves various functions of release 3.2 including a rewrite of the RWTS to make it faster,[6] while allowing for large gains in available floppy disk storage.

To migrate Apple DOS 3.3 files back to version 3.2 disks, someone wrote a "NIFFUM" utility.

This layer consists of subroutines for track seeking, sector reading and writing, and disk formatting.

There is also a CATALOG function, for listing files on the diskette, and an INIT function, which formats a disk for use with DOS, storing a copy of DOS on the first three tracks, and storing a startup program (usually called HELLO) that is auto-started when this disk is booted from.

On top of the File Manager API, the main DOS routines are implemented which hook into the machine's BASIC interpreter and intercept all disk commands.

It provides BLOAD, BSAVE, and BRUN for storing, loading, and running binary executables.

A call vector table in the region of $03D0–03FF16 allows programs to find DOS wherever it is loaded in the system memory.

Apple commissioned Microsoft to develop Applesoft BASIC,[8] capable of handling floating-point numbers.

However, many people who had no need for the improvements of ProDOS (and who did not like its much higher memory footprint) continued using Apple DOS or one of its clones long after 1983.

[9] Commercial games usually did not use Apple DOS, instead having their own custom disk routines for copy protection purposes as well as for performance.

DOS's RWTS routine can read or write a track in two revolutions with proper interleaving.

An early patch to provide this functionality was published in Call-A.P.P.L.E.. Speedups in the LOAD command of three to five times were typical.

This functionality soon appeared in commercial products, such as Pronto-DOS, Diversi-DOS, Hyper-DOS, and David-DOS, along with additional features, but it was never used in an official Apple DOS release.