The data type of an object must be specified in its declaration.
  The fundamental data types are the scalar types:

  short int           16-bit signed integer
  signed short int    16-bit signed integer
  unsigned short int  16-bit unsigned integer
  int                 32-bit signed integer
  signed int          32-bit signed integer
  unsigned int        32-bit unsigned integer
  long int            32-bit signed integer
  signed long int     32-bit signed integer
  unsigned long int   32-bit unsigned integer
  long long int       64-bit signed integer
  signed long long int     64-bit signed integer
  unsigned long long int   64-bit unsigned integer
  char                8-bit signed integer
  signed char         8-bit signed integer
  unsigned char       8-bit unsigned integer
  wchar_t             Long character (32-bit unsigned integer)
  float               32-bit (single-precision) floating-point number
  double              64-bit (double-precision) floating-point number
  long double         128-bit (double-precision) floating-point
                      number
  long float          Interchangeable with double, but usage is
                      obsolete
  _Bool               An unsigned int that has the value 0 or 1
  _Imaginary          A C99-specified data type.  In VSI C, use of
                      the _Imaginary keyword produces a warning,
                      which is resolved by treating it as an ordinary
                      identifier.
  _Complex            C99-specified data type available in all three
                      precisions:  float _Complex, double _Complex,
                      or long double _Complex.  A complex type has
                      the same representation and alignment
                      requirements as an array type containing
                      exactly two elements of the corresponding real
                      type; the first element is equal to the real
                      part, and the second element to the imaginary
                      part, of the complex number.

                      Note:  This complex data type is similar to the
                      Fortran type, and has an associated header
                      file, <complex.h>.  Although the fundamental
                      complex data types are implemented in the
                      compiler, the run-time support will not be
                      available until an OpenVMS Alpha release
                      following Version 7.3.

  The signed keyword is the default.  Declaring an object with int,
  for example, is equivalent to declaring it with signed int.
  However, char declarations should be explicitly declared, as the
  compiler offers command-line options to change the default.  If in
  doubt, use signed char over char because signed char is more
  portable.

  Strings are arrays of characters terminated by the null character
  (\0).

  Also, view the contents of the <ints.h> header file for definitions
  of platform-specific integer types.