Can application programs which work with old versions of the HDF4 library always be compiled with new versions of HDF4?
As HDF evolves some functions have to be changed or removed. For example, in HDF3.2 some functions' formal parameters which were passed by value in HDF3.1 have to be passed by reference in order to support new number types. When this happens, old application programs need to be modified so that they can work with the new library.
Our policy is as follows: Keep existing functions unchanged as much as possible; create new functions when necessary to accommodate new features; if a new function covers the feature of an existing old function, the old function should still be callable by old application programs; should an old function be phased out, the users will be forewarned and encouraged to switch to the new function; an old function will be removed from the library only if it is in conflict with the implementation of new features.