VMS Help  —  FORTRAN  Data  Intrinsic Types
  VSI Fortran provides the following intrinsic data types:

   o  INTEGER (4 kind type parameters) - a whole number

   o  REAL (3 kind type parameters) - a floating point number (a
      whole number, a decimal fraction, or a combination)

   o  DOUBLE PRECISION - a REAL kind type parameter that has more
      than twice the degree of accuracy in its representation, and
      greater range

   o  COMPLEX (3 kind type parameters) - a pair of REAL values
      representing a complex number (the first part of the number is
      the real part, the second is the imaginary part)

   o  DOUBLE COMPLEX - a COMPLEX kind type parameter with DOUBLE
      PRECISION real and imaginary parts

   o  LOGICAL (4 kind type parameters)- a logical value, .TRUE.  or
      .FALSE.

   o  CHARACTER - a sequence of characters

   o  BYTE - a one-byte value equivalent to INTEGER(KIND=1)

1  –  CHARACTER 

  A character string is a contiguous sequence of bytes in memory.  A
  character string is specified by two attributes:  the address of
  the first byte of the string and the length of the string in bytes.
  The length of the string must be in the range 1 through 65535.

  Hollerith constants are stored internally, one character per byte.

2  –  COMPLEX 

  Real and complex numbers are floating-point representations.

  COMPLEX(KIND=4) (or COMPLEX*8) data is eight contiguous bytes
  aligned on an arbitrary byte boundary.  The low-order four bytes
  contain REAL(KIND=4) (or REAL*4) data that represents the real part
  of the complex number.  The high-order four bytes contain REAL data
  that represents the imaginary part of the complex number.  For
  information on the ranges of REAL data, see REAL (within the DATA
  CONSTANTS section of online Help).

  DOUBLE COMPLEX (COMPLEX(KIND=8) or COMPLEX*16) data is 16
  contiguous bytes aligned on an arbitrary byte boundary.  The
  low-order bytes contain DOUBLE PRECISION data that represents the
  real part of the complex number.  The high-order eight bytes
  contain DOUBLE PRECISION data that represents the imaginary part of
  the complex data.  For information on the ranges of DOUBLE
  PRECISION data, see DOUBLE_PRECISION (within the DATA CONSTANTS
  section of online Help).

  COMPLEX(KIND=16) (or COMPLEX*32) data is 32 contiguous bytes
  aligned on an arbitrary byte boundary.  The low-order bytes contain
  REAL(KIND=16) (or REAL*16) data that represents the real part of
  the complex number.  The high-order bytes contain REAL*16 data that
  represents the imaginary part of the complex number.  For
  information on the ranges of REAL*16 data, see REAL (within the
  DATA CONSTANTS section of online Help).

3  –  INTEGER 

  Integer numbers are whole numbers.  For information on the ranges
  of INTEGER data, see INTEGER (within the DATA CONSTANTS section of
  online Help).

  INTEGER*2, INTEGER*4, and INTEGER*8 values are stored in two's
  complement form.

  Note that logical data type ranges correspond to their comparable
  integer data type ranges.  For example, in LOGICAL*2 L, the range
  for L is the same as the range for INTEGER*2 integers.

4  –  LOGICAL 

  Logical values start on an arbitrary byte boundary and are stored
  in one, two, or four contiguous bytes.  The low-order bit (bit 0)
  determines the value.  If bit 0 is set, the value is .TRUE.; if bit
  0 is clear, the value is .FALSE.  The remaining bits are undefined.

  When a logical value is stored in memory, all of its bits are
  stored.  For example, consider the following:

     LOGICAL*4 L1, L2, L3
     L1 = L2 .AND. L3

  This example does a full 32-bit AND of L2 and L3, and stores all 32
  resulting bits in L1.

5  –  REAL 

  Real and complex numbers are floating-point representations.

  The exponent for REAL(KIND=4) (or REAL*4) (F_floating) and DOUBLE
  PRECISION (REAL(KIND=8) or REAL*8) (D_floating) formats is stored
  in binary excess 128 notation.  Binary exponents from -127 to 127
  are represented by the binary equivalents of 1 through 255.

  The exponent for the DOUBLE PRECISION G_floating format and
  T_floating format is stored in binary excess 1024 notation.  The
  exponent for the REAL*16 format is stored in binary excess 16384
  notation.  In DOUBLE PRECISION (G_floating) format, binary exponents
  from -1023 to 1023 are represented by the binary equivalents of 1
  through 2047.  In REAL*16 format, binary exponents from -16383 to
  16383 are represented by the binary equivalents of 1 through 32767.

  For floating-point format, fractions are represented in
  sign-magnitude notation, with the binary radix point to the left of
  the most significant bit for F_floating, D_floating, and G_floating,
  and to the right of the most significant bit for S_floating and
  T_floating.  Fractions are assumed to be normalized, and therefore
  the most significant bit is not stored.  This bit is assumed to be 1
  unless the exponent is 0.  in which case the value represented is
  either zero or is a reserved operand.

  REAL(KIND=4) (or REAL*4) numbers occupy four contiguous bytes and
  the precision is approximately one part in 2**23, that is,
  typically 7 decimal digits.

  DOUBLE PRECISION (D_floating) numbers occupy eight contiguous bytes
  and the precision is approximately one part in 2**55, that is,
  typically 16 decimal digits.

  DOUBLE PRECISION G_floating numbers occupy eight contiguous bytes
  and the precision is approximately one part in 2**52, that is,
  typically 15 decimal digits.

  REAL*16 (H_floating) numbers occupy sixteen contiguous bytes and
  the precision is approximately 2**112, that is, typically 33
  decimal digits.

  For more information on real data type ranges, see DATA CONSTANTS
  REAL and DATA CONSTANTS DOUBLE_PRECISION in this Help file.
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