2. Core, Preprocessor, and Library

Three parts:

1. The core C language

   44 keywords, 49 operators, plus punctuation characters and syntax rules

2. The C preprocessor

   Lines starting with a pound-sign

       #define -- macros
       #include -- other source files
       #ifdef -- conditional compilation
   

3. The C standard library

   29 parts, defined by standard headers:

   assert.h, ctype.h, errno.h, float.h, limits.h, locale.h, math.h, setjmp.h, signal.h, stdarg.h, stddef.h, stdio.h, stdlib.h, string.h, time.h

   complex.h, fenv.h, inttypes.h, iso646.h, stdbool.h, stdint.h, tgmath.h, wchar.h, wctype.h (C99)

   stdalign.h, stdatomic.h, stdnoreturn.h, threads.h, uchar.h (C11)