Continued from Understanding Variables:
Like most programming languages, ActionScript variables follow a set of rules when it comes to naming. ActionScript variable names can have letters, numbers, dollar signs, and underscores, but they cannot start with a number. ActionScript variables are also case-sensitive.
ActionScript variables are a little unusual in that any variable can store any type of data. When a piece of data is assigned to a variable, the interpreter automatically changes the variable type to whatever type the data is. In programming languages like Java and C++, data of the wrong type is converted to the variable’s data type instead of the other way around, or an error is caused in the program.
Alternatively, ActionScript variable types can be set when the variable is declared.
ActionScript 2.0 has several built-in data types:
- Boolean – a data type with only two possible values: true or false
- MovieClip – a special data type used for controlling movie clip instances
- null – a special data value representing an absence of data; default value for variables declared without a value
- Number – any series of numeric values, including integers, unsigned integers, and floating point numbers; mainly used for counting and mathematical equations
- Object – built-in or user-defined classes of data; a collection of properties or attributes
- String – a series of alphanumeric characters, numbers, and punctuation marks
- undefined – same as the null data type; default value for instances of the Object class
- Void – special data type used to designate functions that don’t return a value
ActionScript 3.0 also adds two more data types:
- int – a 32-bit integer between -231 and 231-1
- uint – a 32-bit unsigned integer (either positive or zero) between 0 and 232-1