1. A computer-implemented method, comprising: receiving input specifying a graphical program, wherein the graphical program comprises a plurality of interconnected nodes which visually represents the graphical program; wherein said receiving input specifying the graphical program comprises: receiving input including a structure in the graphical program; and displaying the structure in the graphical program based on the user input; associating at least one node with the structure, wherein the at least one node is executable to modify the value of a global variable; wherein during execution of the graphical program the structure ensures deterministic modification of values of the global variable.