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[christyleomin]

Hi,

I have been debugging someone else's code and have the following question regarding the EQUIVALENCE statement used there;

Can someone please explain what it is supposed to mean? The equivalence statement here?

[LitusSaxonicum]

What it means in EQUIVALENCEing control and kontrol is that they share the same physical addresses in the computer RAM � i.e. they start at the same address. As each is 8 bytes long, and there are 512 of them, it marks out a block of storage that is 4k bytes long. Sometimes this 4k will hold REAL*8 values, and sometimes, INTEGER*8 values. This sort of thing was done in the past. Nowadays, you could ALLOCATE 4k, use it to hold REAL*8 values, then DEALLOCATE it, ALLOCATE 4k again to store INTEGER*8 values and so on. You would take pot luck as to whether you got the same physical memory, but it would work all the same.

My guess is that it is used to store REAL*8 values at a different time to when it stores INTEGER*8 values, as you can�t store in one way and read back in the other.

The other EQUIVALENCE uses the first 80 bytes to store characters � again, the same memory block is being used, but almost certainly not at the same time. As you have so much memory these days, you could simply comment-out the EQUIVALENCE statements and it would probably work OK. (Sometimes you can�t).

This is a trick to cope with being short of RAM � a real problem in the distant past.

There are other uses for EQUIVALENCE. Hopefully you won't encounter them ...

Eddie

[christyleomin]

But, i get junk values for realarray(3) and realarray(4) inspite of the equivalence. Why is it so?

[LitusSaxonicum]

Try this:

[christyleomin]

Last int 4