http://kor.i2p/books/The%20C%20Programming%20Language%20by%20K&R/appb.html
We have omitted a few functions that are
of limited utility or easily synthesized from others; we have omitted
multi-byte characters; and we have omitted discussion of locale issues; that
is, properties that depend on local language, nationality, or culture. The functions, types and macros of the standard library are declared in
standard headers : < assert.h > < float.h > < math.h > < stdarg.h > < stdlib.h > < ctype.h > < limits.h > < setjmp.h > < stddef.h > < string.h > < errno.h > <...