Along with JavaScript variables, PTC Arbortext Layout Developer provides two types of variable — format safe variables and global variables.

Internally, Perl handles global variables. They can be accessed anywhere in the PTC Arbortext Layout Developer instance that is running, even if a document is not open. Once a global variable has been set to a value, the value does not change until a specific action changes it. This is the case regardless of the document that is active or the page position. Global variables have some benefits and uses, but are not used in a formatting context. PTC Arbortext Layout Developer also uses global variables to store some of its own information.

Refer to Global Variables for information.

Format safe variables, or counters, track the formatting process of a given stream. Each content stream being formatted has a set of format safe variables. As each page progresses, PTC Arbortext Layout Developer retains the values of each format safe variable at the top of each frame. With this feature, you can page up and down through a document and PTC Arbortext Layout Developer retains the values of those variables for those positions.

Format safe variables (counters) fall into three groups:

JavaScript variables can also be considered format safe.