Standard Headers assert.h - program diagnostics ctype.h - character testing and case mapping errno.h - error reporting float.h - floating type characteristics limits.h - integral type sizes locale.h - local customs math.h - mathematics setjmp.h - non-local jumps signal.h - signal handling stdarg.h - variable-length arguments lists stddef.h - common definitions stdio.h - input and output stdlib.h - general utilities string.h - string handling time.h - date and time utilities