1. A method of creating a function block in a programming paradigm for use with a process control system implemented at a process plant, comprising: defining in the function block a plurality of data items used by the function block, each data item having an associated attribute the value of which attribute determines whether the data item is public data or private data, wherein data items that are public data are generally available for use by the function block and multiple other function blocks instantiated within the process control system, and wherein data items that are private data are accessible only by the function block; selecting an initialization routine from a plurality of source code files using a computer device associated with the process control system at the process plant, which initialization routine initializes the data items associated with the function block; selecting a periodic execution routine from the plurality of source code files using the computer device associated with the process control system at the process plant; selecting a write checking routine from the plurality of source code files using the computer device associated with the process control system at the process plant, which write checking routine validates data written to the initialized data items from a source outside of the function block; associating the initialization routine, the periodic execution routine and the write checking routine with one another to define the function block within the programming paradigm using the computer device associated with the process control system at the process plant; modifying, using the computer device associated with the process control system at the process plant, one of the initialization routine, the periodic execution routine and the write checking routine to include a logical procedure, defined by source code executable on a processor, which logical procedure is not provided with the selected ones of source code files to thereby provide the function block with new execution functionality; and storing the function block with the new execution functionality as a template function block capable of being used to create an instantiated function block within the process control system at the process plant, wherein the instantiated function block communicatively interacts, within the process control system, with other function blocks that are created using the programming paradigm.