1. A method for propagating type information for hardware device nodes in a graphical program, wherein the method operates in a computer including a display screen and a user input device, the method comprising: displaying on the screen a first hardware device node in the graphical program in response to user input; associating the first hardware device node with a hardware device; displaying on the screen a second hardware device node in the graphical program in response to user input; connecting the first hardware device node to the second hardware device node in response to user input; propagating information from the first hardware device node to the second hardware device node, wherein the information specifies the hardware device with which the first hardware device node is associated, wherein said propagating occurs in response to said connecting the first hardware device node to the second hardware device node.