MACHAR is a FORTRAN90 library which dynamically computes constants that characterize the floating point arithmetic system on a computer, by William Cody.
The constants include the value of the "machine epsilon", the smallest number that can be added to 1 and make a difference. However, it includes many other quantities of interest, including the arithmetic base, the largest and smallest magnitudes, and so on.
The FORTRAN77 version of these routines was supplied as part of ACM TOMS algorithm 665.
A C version of these routines was supplied as part of ACM TOMS algorithm 722.
In FORTRAN90, there are built-in arithmetic functions that can immediately return the values that MACHAR is trying to determine.
If I is an integer value,then:
If X is a single precision real value, or a double precision real value, then:
MACHAR is available in a C version and a C++ version and a FORTRAN77 version and a FORTRAN90 version and a MATLAB version and a Python version.
F90, FORTRAN90 programs which demonstrate features of the FORTRAN90 language, in particular, epsilon(), huge(), and tiny() which evaluate some machine arithmetic quantities directly.
MACHINE, a FORTRAN90 library which store the appropriate values of machine constants for a given machine.
PARANOIA, a FORTRAN90 program which checks the accuracy of floating point arithmetic on a given computer.
Original FORTRAN77 version by William Cody. FORTRAN90 version by John Burkardt.
You can go up one level to the FORTRAN90 source codes.