---
keywords: ["Alto OS", "Xerox", "Alto", 1970s, 1973]
image: ./alto-os.webp
description: "The Xerox Alto OS, was the first GUI system. It was way ahead of its time. We can run it on ContrAlto emulator."
sidebar_position: 1
---

import DocCardList from '@theme/DocCardList';

# Alto OS

![Alto OS](./alto-os.webp)

The Xerox Alto OS, was the first GUI system. It was way ahead of its time. We can run it on ContrAlto emulator.

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## Manuals

:::tip

The manuals refer to the mouse buttons by their color. On a modern 3-button mouse, the colors map as the following:

- Red = Left mouse button
- Yellow = Middle mouse button
- Blue = Right mouse button

On most mouses, pressing the scroll-wheel simulates pressing the middle mouse button.

:::

You can download the Alto OS manuals from [bitsavers](http://bitsavers.org/pdf/xerox/alto/). These are the most useful ones:

- [Alto User's Handbook](http://bitsavers.org/pdf/xerox/alto/Alto_Users_Handbook_Sep79.pdf)
- [Alto Subsystems Manual](http://bitsavers.org/pdf/xerox/alto/AltoSubsystems_Oct79.pdf)
- [Alto Operating System Reference Manual (Part 1)](http://bitsavers.org/pdf/xerox/alto/AltoSWRef.part1.pdf)
- [Alto Operating System Reference Manual (Part 2)](http://bitsavers.org/pdf/xerox/alto/AltoSWRef.part2.pdf)
- [BCPL Reference Manual](http://bitsavers.org/pdf/xerox/alto/bcpl/AltoBCPLdoc.pdf)
- [Bravo Course Outline](http://bitsavers.org/pdf/xerox/alto/BravoCourse.pdf)

You may also be interested in the Alto hardware manual:

- [Alto Hardware Manual (Part 1)](http://bitsavers.org/pdf/xerox/alto/AltoHWRef.part1.pdf)
- [Alto Hardware Manual (Part 2)](http://bitsavers.org/pdf/xerox/alto/AltoHWRef.part2.pdf)

## Apps

- [Preinstalled Apps](/1970s/1973/alto-os/preinstalled-apps/)

## Related Pages

- [VirtualHub Screenshots](https://screenshots.virtualhub.eu.org/1970s/1973/alto-os/)
- [Run Alto OS in your browser: ContrAltoJS](https://archives.loomcom.com/contraltojs/)  (Instructions given on page)
- [Wikipedia](https://en.wikipedia.org/wiki/Xerox_Alto#Software)
- [Computer History Wiki Alto page](https://gunkies.org/wiki/Xerox_Alto)
- [Toasty Tech Xerox Alto page](http://toastytech.com/guis/alto.html)
- [Toasty Tech page on running Alto OS on the older `salto` emulator](http://toastytech.com/guis/salto.html)
- [Computer History Museum: Xerox Alto Source Code Release](https://computerhistory.org/blog/xerox-alto-source-code/)

## Credits

- The manuals were taken from [Bitsavers](http://bitsavers.org).