HP Fortran Programmer's Reference (September 2007)

Intrinsic procedures
Data representation models
Chapter 11 507
Data representation models
The Fortran 90 Standard specifies data representation models that suggest how data are
represented in the computer and how computations are performed on the data. The
computations performed by some Fortran 90 intrinsic functions are described in terms of
these models.
There are three data representation models in Fortran 90:
• “The Bit Model” on page 508
• “The Integer Number System Model” on page 509
• “The Real Number System Model” on page 509
In any given implementation, the model parameters are chosen to match the implementation
as closely as possible. However, an exact match is not required, and the model does not impose
any particular arithmetic on the implementation.
Data representation model intrinsics
Several intrinsic functions provide information about the three data representation models.
These intrinsics are listed in Table 11-2.
Table 11-2 Intrinsic functions and data representation models
Intrinsic function Description
“BIT_SIZE(I)” on page 531 Number of bits in an integer of the kind of I (I is an
object, not a kind number)
“DIGITS(X)” on page 543 Base digits of precision in integer or real model for X
“EPSILON(X)” on page 549 Small value compared to 1 in real model for X
“EXPONENT(X)” on page 550 Real model exponent value for X
“FRACTION(X)” on page 552 Real model fraction value for X
“HUGE(X)” on page 555 Largest model number in integer or real model for X
“MAXEXPONENT(X)” on page 588 Maximum exponent value in real model for X
“MINEXPONENT(X)” on page 593 Minimum exponent value in real model for X
“NEAREST(X, S)” on page 599 Nearest processor real value