Re: help needed, ada project

["David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>]

michaelb wrote in message <36b0501a.0@interalpha.net>...
>hello my name is mike and am in desperate need for some help
>I am currently on a BTEC HND in computing and I have a peice of
>coursework that is in jeopardy as i have no understanding of the direct_io
>file format, could somebody send me some basic examples of this so
>that I can complete my course work,
>
>michaelb@interalpha.co.uk
>
>any help would be most appreciated.
>
>p.s. the ada development environment i am using is ada95, i dont
>think that there any major differances between this and vax ada.
>
Instantiations of both Direct_IO and Sequential_IO read and write raw binary
files consisting of some quantity of records of the memory images of the
type with which they were instantiated.

Although I am unaware of any requirements for a specific file format, all of
the implementations for which I have examined the files have nothing to
delimit the records -- i.e., there are just repetirions
of the memory images of the data items which were written.

Thus, these files can only be read by a program compiled with a compiler
which lays out the type
in memory the same way -- whether by default, or by having written the
programs with
representation clauses on the types which force a particular layout.

In practice, this usually means reading and writing on the same platform
type, using programs compiled by the same compiler.

The only difference between Sequential_IO and Direct_IO, is that Direct_IO
allows reading and writing
with random access -- i.e., by specifying the record number to read or
write, while Sequential_IO
is just that -- sequential.

I hope this helps.

Davis C. Hoos, Sr.