The _tolower() macro shall be equivalent to tolower(c)
except that the application shall ensure that the
argument c is an uppercase letter.
Upon successful completion, _tolower() shall return the lowercase
letter corresponding to the argument passed.
No errors are defined.
The following sections are informative.
tolower() , isupper() , the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 7, Locale, <ctype.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at