These are functions that do not perform any locking. They are provided for users requiring maximum performance. For more information, see Multithreaded Libraries Performance.
Use _nolock functions only if your program is truly single-threaded or if it does its own locking.
_fseek_nolock, _fseeki64_nolock
_ftell_nolock, _ftelli64_nolock
_getchar_nolock, _getwchar_nolock
_getche_nolock, _getwche_nolock
_getdcwd_nolock, _wgetdcwd_nolock
_putchar_nolock, _putwchar_nolock
_ungetc_nolock, _ungetwc_nolock
_ungetch_nolock, _ungetwch_nolock