App Inventor is a web application that lets you develop applications for Android devices (smartphones or tablets) using a visual programming language. It is free and open source software.

To work with the App Inventor you must have:

• a Google account,
• a computer with Internet access,
• a compatible browser (Mozilla Firefox, Apple Safari, Google Chrome - Microsoft Internet Explorer is not supported).

If you have problems with internet connection or logging with a Google account you can use App Inventor 2 Ultimate.

App Inventor saves the projects to cloud storage under the name of your Google account. You do not need to save projects in your local disk drive.

An App Inventor application consists of the Component Designer and the Blocks Editor. At the App Inventor Designer you can create the application’s screens by arranging the elements (components) of the application. At the App Inventor Blocks Editor you can program the component’s behavior by snapping code blocks. Blocks represent commands that specify an action to be performed.

There are two types of components: visible and non-visible. Visible components (like Buttons, Labels, Text Boxes) are those that you can see when the application is launched and are part of the application user interface. Non-visible components (like Accelerometer, Sound, OrientationSensor) are not seen and provide access to the built-in functionality of the device. They are not part of the user interface.

You can create more than one screen to an application but you must be cautious because every screen consumes computer resources. Every screen has its name and its properties. As a rule of thumb, you should not have more than 10 screens per project.

If you do not have an Android phone or tablet to connect to your computer, you can still develop and test apps with App Inventor. App Inventor provides an Android emulator, which installs a virtual Android device on your computer screen and works just like an Android device.