Apple DOS 3.3

Apple’s DOS 3.3 was a game-changer for personal computers in 1980. As the first widely used disk operating system, it brought new levels of storage and functionality to the Apple IIe computer.

Released on August 25, 1980, Apple DOS 3.3 improved upon the previous version, 3.2, by increasing the available storage on floppy disks. The P5A/P6A PROMs in the disk controller allowed for data to be read and written at a higher density, resulting in 16 sectors (4 KiB) of data per disk track, as opposed to 13 sectors (3.25 KiB) in 3.2. This increased the capacity from 113.75 KB to 140 KB per disk side, with 124 KB available for user programs and data.

However, there was a catch. DOS 3.3 was not backward compatible, meaning it could not read or write 3.2 disks. To address this issue, Apple released a utility called “MUFFIN” to migrate 3.2 files and programs to version 3.3 disks. Unfortunately, there was no utility for migrating files back to 3.2 disks.

In addition to increased storage, release 3.3 also improved the ability to switch between Integer BASIC and Applesoft BASIC with the use of a language card or firmware card.

By 1983, Apple DOS 3.3 had been replaced by ProDOS 8. But despite its age, the legacy of this revolutionary operating system lives on, 42 years later.

Apple DOS 3.3
Source: – Apple DOS 3.3

Apple DOS 3.3 General Information

IntroducedAugust 25, 1980
System RequirementsApple IIe
DistributionFloppy disk

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