MACHAR - Dynamically Compute Machine Constants

MACHAR is a routine to compute constants that characterize the floating point arithmetic system on a computer. This includes 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 original routine was written in FORTRAN, and a copy of that is available in the FORTRAN MACHAR directory. A C "translation" was supplied as part of ACM algorithm 722, and that is what is given here.

Reference 1:

W J Cody,
ACM Algorithm 665, MACHAR, a subroutine to dynamically determine machine parameters,
ACM Transactions on Mathematical Software,
Volume 14, Number 4, pages 303-311, 1988.

Reference 2:

W J Cody and W Waite,
Software Manual for the Elementary Functions,
1980.

Files you may copy include:

• machar.c, the source code.
• machar.h, the include file.
• machar_prb.c, a sample problem.
• machar_prb.out, sample problem output.

The list of routines includes:

• MACHAR_S determines single precision machine constants.
• MACHAR_D determines double precision machine constants.

Return to the C software page.

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Last revised on 19 November 2001.