number next to a variable - allowed? 1

[philrosenberg]

Hi I'm trying to find a bug in a FORTRAN program my office has purchased, but as a person who has not used fortran before I'm hoping someone may be able to give me a couple of hints.

One line of the code is

TRM1 = 1.0D0 - DFXDT * (2.0D0 - DFXDT)

where TRM1, D0 and DFXDT are all variables. The problem is that noone in our office has seen the notation 1.0D0 before, does anyone know what it does?

Thanks for any help

Phil

 

[CaKiwi]

1.0D0 is scientific notation "one times ten to the power of zero" which computes to be just one. It is usually written that way to emphasise the fact that it is a double precision value. D0 is not a variable.

CaKiwi

"I love mankind, it's people I can't stand" - Linus Van Pelt

 

[philrosenberg]

thanks for the reply CaKiwi. At first I thought something similar but this line was just above it

BETA0 = D0 * DPDD / P0

which made me think D0 was a variable, any idea what this then means if D0 is not a variable?

Thanks again

Phil

 

[CaKiwi]

Just to confuse you, if D0 is used by itself and not preceeded by a number, it is a variable.

CaKiwi

"I love mankind, it's people I can't stand" - Linus Van Pelt

 

[philrosenberg]

Thank you very much, you've been extremely helpful and patient.

Thanks again

Phil

 

[xwb]

1.0D0 is for double precision
1.0E0 is for real

The meaning of double precision has changed a lot since my student days. It can mean

o more significant digits
o a larger range of numbers than reals
o both of the above