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Origins of Apple's DOS code

SANTA CRUZ MOUNTAINS, Calif. -- Without a disk drive, the Apple II might never have become one of the most iconic computers in history. But Apple desperately needed a disk operating system to run its hard drives. Newly surfaced documents illustrate the process that led to the creation of that DOS.

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The original Apple DOS documents, April 10, 1978

Communications between Apple's Steve Jobs and developer Robert Shepardson discuss the components of the Apple II disk operating system, including a file manager, a BASIC and Applesoft BASIC interface, and disk copying, recovery, and backup utilities.

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Modifications

This letter from Shepardson to Jobs on June 26, 1978, states the changes on the development work which will be delivered in just one day, for a cost of $500.

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Damer at the DigiBarn

Bruce Damer, founder of the DigiBarn computer museum in the Santa Cruz Mountains of California, talks about the documents, and about the history of the Apple II computer.

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A disk operating system for $13,000

The price paid to the developer for building the first Apple OS? $13,000. With no additional royalties.

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A list of modifications

Hand-written documents list modifications Apple needed to the DOS in June 1978. The new operating system was to be rolled out that October.

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Just eight chips

Over Christmas of 1977 Woz designed this single board interface to run two floppy drives. He did it with just eight chips, while other disk controllers usually needed dozens.

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More modifications

Another document showing modifications to the DOS required by Apple.

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Breakout on cassette

For the first year of the Apple II, users had only a cassette drive to load or save with.

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Bugs memo

This memo detailed some of the debugging work that would be done on the new Apple disk operating system.

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Price list

An official price list for the Apple II.

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DigiBarn's Damer is frequently sent unsolicited pieces of computer history. He had no idea what the Apple DOS documents, sent to him by developer Paul Laughton, contained when he received them.

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Instructions

Hand-written instructions for the Apple DOS.

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Apple II disk

A 5.25-inch floppy disk for the Apple II. Without the Apple DOS, which the company commissioned from Shepardson Microsystems, Apple might never have become the computer giant we know today.

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The controller

The disk controller Wozniak designed held up against a schematic for its design.

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Woz's innovative disk controller

Steve Wozniak's circuit diagrams for his floppy disk controller -- which are considered groundbreaking among computer history experts -- alongside one of the actual boards.

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Woz specs

In the upper right corner of the sheet in front, you can see that this was a diagram by Steve Wozniak. It is the design spec for his groundbreaking disk drive controller.

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Head step timing

A document spells out the head step timing for the Apple disk operating system.

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Pin assignments

Apple disk controller pin assignments from the original disk operating system code.

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Original code

Damer and the DigiBarn are hoping to find volunteers willing to hand-code the original DOS program.

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Human translation

Apple DOS code printed out. The right column shows the human translation of what the command does.

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To be read by actual people

More of the Apple DOS code printed out.

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