The characterization as obsolescent of the use of the ``old style'' function declarations and definitions --- that is, the traditional style not using prototypes --- signals the Committee's intent that the new prototype style should eventually replace the old style.
The case for the prototype style is presented in
§
and §.
The gist of this case is that the new syntax addresses
some of the most glaring weaknesses
of the language defined in the Base Document,
that the new style is superior to the old style on every count.
It was obviously out of the question to remove syntax used in the overwhelming majority of extant C code, so the Standard specifies two ways of writing function declarations and function definitions. Characterizing the old style as obsolescent is meant to discourage its use, and to serve as a strong endorsement by the Committee of the new style. It confidently expects that approval and adoption of the prototype style will make it feasible for some future C Standard to remove the old style syntax.
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