Helping Kids with Coding For Dummies
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Your young coder can write code that changes the value of a variable under certain conditions as the program executes. A common way to change a variable value is to increment it. To increment a variable means to increase it by the same amount at each change. For example, your coder may increment a scoring variable by +2 each time a basketball goal is made. Decreasing a variable in this way is known as decrementing the variable value. Your coder may decrement a timer by –1 each time one second on the clock elapses.

Using pseudocode

The general format for incrementing or decrementing a variable value is as follows:
Action Pseudocode Examples
Increment a variable variable = variable + change score = score + 1

numTwins = numTwins + 2
Decrement a variable variable = variable - change timeRemaining = timeRemaining - 1

cost = cost - 5
Boolean variables aren't incremented nor decremented. A Boolean variable exists only in one of two states: true or false.

Using Scratch

To increment or decrement a variable in Scratch, follow these steps:
  1. Go to the Data blocks code tile category.
  2. Select the change <em>variable name</em> <em>by </em><em>value</em> code tile and drag it into your program.
  3. Press the tab beside the variable name and select the variable whose value you want to change.
  4. Type a number for the increment or decrement in the value field. Use a positive number to increment the value. Use a negative number to decrement the value.
variable value coding Changing a variable value in Scratch.

Using Python

To increment a variable value in Python, type the code

<em>variableName = variableName + value</em>

at the location in your code where you want to change the value.

To decrement a variable value Python, type the code

<em>variableName = variableName – value</em>

at the location in your code where you want to change the value.

Using JavaScript

To increment a variable value in JavaScript, type the code

<em>variableName = variableName + value;</em>

at the location in your code where you want to change the value.

To decrement a variable value in JavaScript, type the code

<em>variableName = variableName – value;</em>

Using Java

To increment a variable value in a Java program, type the code

<em>variableName = variableName + value;</em>

at the location in your code where you want to change the value.

To decrement a variable value in a Java program, type the code

<em>variableName = variableName – value;</em>

About This Article

This article is from the book:

About the book authors:

Camille McCue, PhD, is Director of Curriculum Innovations at the Adelson Educational Campus in Las Vegas where she leads the Startup Incubator, teaches STEM, and kickstarts K-12 learning initiatives. Sarah Guthals, PhD, co-founded an ed-tech company and now continues to build technology for kids to learn, create, and share safely online. She loves to teach teachers how to teach coding in the classroom.

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