15.1.1 ISO C
The ISO C standard first appeared in 1989 (the standard is often called
ANSI C). It added several new features to the C language, most notably
function prototypes. This led to many years of portability issues when
deciding whether to use ISO C features.
We think that programs written today can assume the presence of an ISO C
compiler. Therefore, we will not discuss issues related to the
differences between ISO C compilers and older compilers--often called
K&R compilers, from the first book on C by Kernighan and Ritchie. You may see
these differences handled in older programs.
There is a newer C standard called `C9X'. Because compilers that support it
are not widely available as of this writing, this discussion does not