Abstract: A type definition ability in a graphical programming environment which enables a user to assign a name to a custom control that the user intends to use throughout one or more virtual instruments. The user can create a master or original of a control and use copies of that control in all subsequent virtual instruments. If a user subsequently needs to change that control, the user merely updates the single master control which was saved as a type definition. This has the effect of updating all other copies of that control to that of the changed master or original control. An auto-update feature is included which allows a user to choose between automatic updating of all type definition copies or merely indicating to the user which controls need to be updated. Strict type definitions are provided wherein virtually any user change made to a parameter of the original typedef, i.e. appearance, propagates throughout the remaining instances or copies where that type definition is used.