Arrays
Summary
Materials
Instructional Activities and Classroom Assessments
- Introduce Arrays (15 minutes)
- Activity: Create and Modify Arrays (35 minutes)
- Extension
- Reflection/Homework
Learning Objectives
- AAP-1.A Represent a value with a variable. 3.A
- AAP-1.C Represent a list or string using a variable. 3.A
- AAP-3.E For generating random values:
- a. Write expressions to generate possible values. 2.B
- b. Evaluate expressions to determine the possible results. 4.B 2.B
- AAP-1.D For data abstraction:
- a. Develop data abstraction using lists to store multiple elements. 3.B
- b. Explain how the use of data abstraction manages complexity in program code. 3.C
Essential Knowledge
- AAP-1.A.1 A variable is an abstraction inside a program that can hold a value. Each variable has associated data storage that represents one value at a time, but that value can be a list or other collection that in turn contains multiple values.
- AAP-1.A.2 Using meaningful variable names helps with the readability of program code and understanding of what values are represented by the variables.
- AAP-1.A.3 Some programming languages provide types to represent data, which are referenced using variables. These types include numbers, Booleans, lists, and strings.
- AAP-1.A.4 Some values are better suited to representation using one type of datum rather than another.
- AAP-1.C.1 A list is an ordered sequence of elements. For example, [value1, value2, value3, ...] describes a list where value1 is the first element, value2 is the second element, value3 is the third element, and so on.
- AAP-1.C.2 An element is an individual value in a list that is assigned a unique index.
- AAP-1.C.3 An index is a common method for referencing the elements in a list or string using natural numbers.
- AAP-3.E.1 The exam reference sheet provides RANDOM(a, b) Block: RANDOM a, b which generates and returns a random integer from a to b, inclusive. Each result is equally likely to occur. For example, RANDOM(1, 3) could return 1, 2, or 3.
- AAP-1.D.1 Data abstraction provides a separation between the abstract properties of a data type and the concrete details of its representation.
- AAP-1.D.2 Data abstractions manage complexity in programs by giving a collection of data a name without referencing the specific details of the representation.
- AAP-1.D.3 Data abstractions can be created using lists.
- AAP-1.D.8 The exam reference sheet describes a list structure whose index values are 1 through the number of elements in the list, inclusive. For all list operations, if a list index is less than 1 or greater than the length of the list, an error message is produced and the program will terminate.
Details
1. Introduction to Arrays (15 minutes)
- Define lists in computer science.
- Explain how lists are used.
- Demonstrate how to create a list in MakeCode.
- Discuss lists on the Exam Reference Sheet.
- Explain the difference between how arrays in MakeCode begin at index 0 and how on the AP exam lists begin at index 1.
- Examine the different type of array procedures.
- Discuss existing types of algorithms using lists and iteration.
2. Activity: Create and Modify Arrays (35 minutes)
- Direct students to the Arrays Work page.
- Students will go to the Activity: Arrays Intro webpage.
- Instruct students to complete Tasks 1-2.
- Encourage students to publish their work and paste the links on their Arrays Work page.
3. Extension
- If students finish early, they can complete the extension activity.
- Encourage students to use JavaScript or Python to create the projects from Task 1 and 2.
- You can also encourage students to incorporate these concepts into an existing project.
4. Reflection/Homework
If you run out of time, you may also assign this as individual homework. Students should complete their reflection.
- What is the difference between creating an array of numbers and storing multiple values as individual variables (as in, value1 = 1, value2 = 2, value3 ...)?
- What can an array do that storing different variables by themselves cannot?
- How does the length of an array relate to the position of the final element?