Richard Maine said:
> Did Malcolm say that the data is not actualy read from the disk?
Not as such, but that does not mean that data is necessarily going to
be actually read from the disc.
And in any case, "reading the data into a user variable" involves multiple
copying operations, typically from the disc to a system-address-space
buffer, from there to a user-address-space buffer, sometimes from there
into another user-address-space buffer, and finally into the user variable.
Even if "READ(11)" bypasses only the latter (which I'm sure you'll agree is
virtually guaranteed, since there is no user variable!) it will still
almost certainly have better performance than the READ with a user variable
specified. This is even if the i/o support library was not written with
the thought of optimising "record skipping" in mind.
Cheers,
--
...........................Malcolm Cohen, NAG Ltd., Oxford, U.K.
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