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chromium/chrome/test/data/extensions/calculator_app/README.md 

# Calculator

A sample application that provides a simple calculator. Supports basic
operations such as addition, multiplication, subtraction and division.

This sample also incorporates an MVC-style structure.

## APIs

* [Runtime](http://developer.chrome.com/trunk/apps/app.runtime.html)
* [Window](http://developer.chrome.com/trunk/apps/app.window.html)