Variables

We use the term variable the same as it is used in mathematics and in other programming languages: a named value that can be changed (varies). Variables can be created in several different ways.

• Some blocks such as count with and for each use a variable and defines its values. A traditional computer science term for these are loop variables.
• User-defined functions (also known as "procedures") can define inputs, which creates variables that can be used only within the function. These are traditionally called "parameters" or "arguments".
• Users may create variables at any time through the "set" block. These are traditionally called "global variables". Blockly does not support local variables.

Dropdown menu

Clicking on a variable's dropdown symbol (triangle) gives the following menu:

The menu provides the following options.

• the names of all existing variables defined in the program.
• "Rename variable...", changes the name of this variable wherever it appears in the program. Selecting this option opens a prompt for the new name.
• "Delete the variable...", deletes all blocks that reference this variable wherever it appears in the program.

Blocks

Set

The set block assigns a value to a variable, creating the variable if it doesn't already exist. For example, this sets the value of the variable named "age" to 12.

Get

The get block provides the value stored in a variable, without changing it.

It is possible, but a bad idea, to write a program in which a get appears without a corresponding set.

Change

The change block adds a number to a variable.

This is a shortcut for the following construct.

Example

Consider the following example code:

The first row of blocks creates a variable named "age" and sets its initial value to the number 12. The second row of blocks gets the value 12, adds 1 to it, and stores the sum (13) into the variable. The final row displays the message: "Happy birthday! You are now 13"