1. A method for creating a first graphical program, the method comprising: displaying a first I/O node in the first graphical program, wherein the first I/O node includes associated generation code for programmatically generating execution-time code associated with the first I/O node; receiving first input to select a first I/O source or target corresponding to the first I/O node; and the generation code associated with the first I/O node executing to programmatically generate first execution-time code based on the first input, wherein the programmatically generated first execution-time code is associated with the first I/O node in the first graphical program, and wherein the programmatically generated first execution-time code is executable to provide I/O to or from the first I/O source or target.