"C" locale is the minimal locale. It is a rather neutral locale which has the same settings across all systems and compilers, and therefore the exact results of a program using this locale are predictable. This is the locale used by default on all C programs.<cstring> (<string.h>), functions strcoll and strxfrm are affected by character transformation rules.<cctype> (<ctype.h>), all functions except isdigit and isxdigit are affected by the extended character set selected.<cstdio> (<stdio.h>), formatted input/output operations are affected by character transformation rules and decimal-point character set in the numeric formatting settings.<ctime> (<time.h>), the function strftime is affected by the time formatting settings.