Editing Forth (programming language) (section)

===Data objects===
When a word is a variable or other data object, the CF points to the runtime code associated with the defining word that created it. A defining word has a characteristic "defining behavior" (creating a dictionary entry plus possibly allocating and initializing data space) and also specifies the behavior of an instance of the class of words constructed by this defining word. Examples include:

;<code>VARIABLE</code>
:Names an uninitialized, one-cell memory location. Instance behavior of a <code>VARIABLE</code> returns its address on the stack.
;<code>CONSTANT</code>
:Names a value (specified as an argument to <code>CONSTANT</code>). Instance behavior returns the value.
;<code>CREATE</code>
:Names a location; space may be allocated at this location, or it can be set to contain a string or other initialized value. Instance behavior returns the address of the beginning of this space.

Forth also provides a facility by which a programmer can define new application-specific defining words, specifying both a custom defining behavior and instance behavior. Some examples include circular buffers, named bits on an I/O port, and automatically indexed arrays.

Data objects defined by these and similar words are global in scope. The function provided by local variables in other languages is provided by the data stack in Forth (although Forth also has real local variables). Forth programming style uses very few named data objects compared with other languages; typically such data objects are used to contain data which is used by a number of words or tasks (in a multitasked implementation).<ref name="ceEJ3">{{cite book | title = {{harvnb|Brodie|1987}} | pages = 241 | chapter = Under The Hood | quote = To summarize, there are three kinds of variables: System variables contain values used by the entire Forth system. User variables contain values that are unique for each task, even though the definitions can be used by all tasks in the system. Regular variables can be accessible either system-wide or within a single task only, depending upon whether they are defined within <code>OPERATOR</code> or within a private task.}}</ref>

Forth does not enforce consistency of [[data type]] usage; it is the programmer's responsibility to use appropriate operators to fetch and store values or perform other operations on data.