reserved words

There are a number of words that cannot be used for anything other than their intended use.

C89 has 32 reserved words:

  • auto
  • break
  • case
  • char
  • const
  • continue
  • default
  • do
  • double
  • else
  • enum
  • extern
  • float
  • for
  • goto
  • if
  • int
  • long
  • register
  • return
  • short
  • signed
  • sizeof
  • static
  • struct
  • switch
  • typedef
  • union
  • unsigned
  • void
  • volatile
  • while

C99 added 5 more:

  • _Bool
  • _Complex
  • _Imaginary
  • inline
  • restrict

C11 added 7 more:

  • _Alignas
  • _Alignof
  • _Atomic
  • _Generic
  • _Noreturn
  • _Static_assert
  • _Thread_local

The keyword entry was a reserved word but is no longer.