What is a list?
Many apps use lists of data. For example, a game may keep a list of high scores and your Facebook app keeps a list of your friends.
Lists are a type of data structure used in every programming language, not just App Inventor. We use lists to create and manipulate different sets of values/elements.
What is an index?
The position of an element in a list is called its index. In App Inventor, the first element in a list is index 1. In the figure below, a has index 1, b has index 2, and a has index 3.
![](http://appinventor.mit.edu/explore/sites/all/files/UserGuide/concepts/lists/List.png)
What this means is that we can reference a specific element inside our list if we know which index it has and what the list name is.
App Inventor Lists
In App Inventor, it may be useful to have a list to store data such as numbers in your phone, replies for the Magic Eight Ball app, or the names of people you meet at a conference.
We make lists by using the make a list block. This block is a mutator and can be expanded or shrunk by clicking the blue plus sign. Watch the following gif for more details on how to use this block.
![](http://appinventor.mit.edu/explore/sites/all/files/UserGuide/concepts/makealist.gif)
App Inventor also provides blocks to do many other actions to lists. For more information on the List blocks, check out the List blocks information page.
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