# Arrays: Working with groups of objects

The goal of this lesson is to learn to use arrays (lists) to act on groups of objects together.
You will learn to create an array of strings, numbers and objects.
You will learn to use the control structures that operate on arrays.

An array is a list. When you declare an array in Alice, you can select to make it an array.

The variable greeting is not an array, it is a scalar. It has a single value, "Hello World". When the tortoise says greeting, he says "Hello World"

The variable sayings is an array. The items in an array are numbered starting with 0. The number is called the index or subscript. When you use an array you need to use a subscript to specify which item, or element, in the list is to be used.

In this example, the tortoise says sayings[0], of "Ready".

An array can also use variables as the subscript:

In this example, num is 1, so when the tortoise says sayings[num] he says "Set".

In this module, you will declare and use arrays. An array is a variable that is a list.
You will create arrays of words, numbers, or objects, then use loops to process the entire array.
In order to do this you will:

• Declare a variable to be an array.
• Use subscripts or index to access the elements of the array.
• Utilize loop control structures to process all of the elements of the array.
• Create and process arrays of different data types, including arrays of objects.
• Understand the purpose of parallel arrays and ways to use them.
• Experiment with arrays of segments, such as the segments of an elephants trunk or tail.

### Print the lesson

1. Arrays: Ready, Set, Go!: Tortoise says "Ready", "Set", "Go" using array
2. An array of animals: An array of SJointedModel contains, yeti, tortoise and stuffedTiger
3. The animals talk: Parallel Arrays: One array contains animals, the other the things they say
4. Who's the tallest?: People are in an array, a loop is used to find the tallest.
5. Animals counting: An array of animals take turns to count
6. Segments of an elephant's trunk as an array: The segments of an elephants trunk, tail and a few other things are an array.
7. Self Study Questions
8. Discussion Questions

#### Active Learning

Create a project using arrays