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Christmas Gift Guide

Origins of Apple's DOS code

The original Apple DOS documents, April 10, 1978

Modifications

Damer at the DigiBarn

A disk operating system for $13,000

A list of modifications

Just eight chips

More modifications

Breakout on cassette

Bugs memo

Price list

Instructions

Apple II disk

The controller

Woz's innovative disk controller

Woz specs

Head step timing

Pin assignments

Original code

Human translation

To be read by actual people

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.
Caption by / Photo by James Martin/CNET
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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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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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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The price paid to the developer for building the first Apple OS? $13,000. With no additional royalties.
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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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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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Another document showing modifications to the DOS required by Apple.
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For the first year of the Apple II, users had only a cassette drive to load or save with.
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This memo detailed some of the debugging work that would be done on the new Apple disk operating system.
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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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Hand-written instructions for the Apple DOS.
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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 disk controller Wozniak designed held up against a schematic for its design.
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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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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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A document spells out the head step timing for the Apple disk operating system.
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Apple disk controller pin assignments from the original disk operating system code.
Caption by / Photo by James Martin/CNET
Damer and the DigiBarn are hoping to find volunteers willing to hand-code the original DOS program.
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Apple DOS code printed out. The right column shows the human translation of what the command does.
Caption by / Photo by James Martin/CNET
More of the Apple DOS code printed out.
Caption by / Photo by James Martin/CNET
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