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here is a post from Carlie Coats > > > > Hi. I am teaching a Fortran class and I was wondering... > > > > Is there any use for specifying kinds for constants? > > * YES!! * > > Consider that if you want a full-precision PI, then even on a > REAL*8/REAL*16 machine (like a Cray y/C90/T90), the following > is valid (assuming old-style free-form source, and giving an > example which also ports to "f77") and portably illustrates an > interesting point: > > DOUBLE PRECISION PI > PARAMETER ( PI = 3.14159 26535 89793 23846 26433 83279 D0 ) > > is OK and will get you all MIN( machine-precision, 31 ) significant > digits; however, leave off the "D0" specifying that it is a > double-precision constant and on an IEEE REAL*4/REAL*8 machine you have > said "Take this constant, force it to single-precision, and then stuff > it into double-precision parameter PI", with a net precision of 7 > digits, losing the next 10 significant digits that you almost certainly > wanted. > > Carlie J. Coats, Jr. [log in to unmask] > MCNC Environmental Programs phone: (919)248-9241 > North Carolina Supercomputing Center fax: (919)248-9245 > 3021 Cornwallis Road P. O. Box 12889 > Research Triangle Park, N. C. 27709-2889 USA > "My opinions are my own, and I've got *lots* of them!" > > ------------------- Ian [log in to unmask] Home page http://www.kcl.ac.uk/kis/support/cit//fortran/ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%