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[LitusSaxonicum]

Sid,

To complement Paul's answer, you can also use the OPTIONS compiler directive to set the default REAL to be DOUBLE PRECISION or REAL*8, and something similar to make all INTEGERs 4 byte:

OPTIONS (INTL, DREAL)

Although REAL*4 is good enough precision in many cases, there are also many cases where it isn't. The option DREAL makes it appear as though the computer only has REAL*8 - unless you declare something specifically to a lower precision.

Eddie

[IanLambley]

Is the extended precision going to be available in FTN95? It seems to have been added in the 2008 "iso_fortran_env".

[LitusSaxonicum]

Ian,

By 'extended precision' do you mean REAL*10 ? I remember Paul saying that it's there in 32 bit, but not in 64 bit FTN95.

Eddie

[IanLambley]

Eddie,
You are correct, there is a Real*10 option available in 32-bit as the intel 8086 co-processor supported this resolution directly. It was not ported to the 64-bit version. I was really talking about the Real*16 data type that we had in VAX Fortran-77 all those years ago. In that there was the option to compile with the "Grand" and "Huge" precision allowing either a very high precision but a lower range than the other option which allowed for larger values but with a lower precision. Obviously, they were for sending spacecraft to the moon and further. They also had uses in transfer matrix type of vibration analysis where the determinant of the final matrix involved subtracting the multiple of two large numbers from the multiple of two other large numbers and adjusting a frequency so that they would result in a zero value, thus identifying a natural frequency. This is something our company used for the analysis of the whirling of ship's propeller shafts.
I had just hoped that it would appear in FTN95, although it appears that it is only in the later Fortran standards.

[PaulLaidler]

We are currently working towards implementing extended precision for the x64 platform but it seems unlikely that this will be finished in time for the next full release.

Initially it could be real*10 with real*16 coming later.

The extension may require the use of third party redistributables that would need to be downloaded by the user.

[LitusSaxonicum]

I was just getting my camera ready to take some photos at a formal dinner tonight, and I chose a 128Gb microSD card. Your mention of VAX takes me back. If I go further back to my days of using an Elliot/NCR 4120 or an ICL 1900 series machine, both with 32k words of memory, and respectively tapes or an 8Mb disk, then I�m back in the days of it being impossible to use DOUBLE PRECISION for all but a few named variables. It was worse with the 16k IBM 1130.The concept of a megabyte was alien, and a Gigabyte unimaginable. The idea that storage on the microSD card scale would be achievable � ever � was a pipedream.
At least the word length on the 4120 and 1900 series machines was 24 bits, so 2-word standard REAL was effectively REAL*6. I remember being told by Zienkiewicz (who I met at couple of times at the Institution of Civil Engineers in London) that in the early days of the numerically-integrated isoparametric finite elements, some Americans thought his results were fake as they couldn�t reproduce them using (effectively) REAL*4. At Swansea Zienkiewicz�s people were running stuff on another ICL 1900 machine.
Things ran brilliantly on the London Uni CDC machines with their 60-bit words. REAL*8 is even better. I sometimes wonder about REAL*10 or more, and what sort of calculations demand those precisions.

[IanLambley]

Ah yes, the olden-golden days of ICL 1900s, Maximop and George 3. That is what I used at Sunderland Poly. When the computer was shown to us when I started there in 1973, the operator turned up the volume control on the teletype console so we could hear the data and address bus. Seemingly they used it to tell whether a job was stuck in a loop! They also had an Elliot 803a.
Times have changed.
I used Real*10 for the "Whirling of Shafts" program on a PC, in the absence of Real*16. It actually worked but the program is now effectively scrapped as it is not available in the new FTN95-X64.

As an aside, here is the chorus of a television program signature tune:

Oh what happened to you?
Whatever happened to me?
What became of the people we used to be?
Tomorrow's almost over, today went by so fast
It's the only thing to look forward to, the past

I'm sure you can guess the program.

I have a couple of MicroVax which I'm trying to give to a museum along with my 1980 Acorn Atom!!

Regards
Ian

[mecej4]

[mecej4]

[mecej4]