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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: How do I write directly to a memory address?
Date: Tue, 8 Feb 2011 18:13:21 -0600
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2011-02-08T18:13:21-06:00
List-Id: <comp.lang.ada>

"Shark8" <onewingedshark@gmail.com> wrote in message 
news:ee766e88-e4c4-4278-8b05-fd0dc9aa3fdb@k17g2000pre.googlegroups.com...
>> How do you test the third bit of a byte in Ada?
>
>One Way, assuming a 1..8 numbering for an 8-bit byte:

Presuming I *wasn't* interviewing for a job, would be to point out that that 
is the wrong question. The question is typically something like testing the 
ready bit in a device. And the solution to that in Ada is to map the device 
to an appropriate record type, and then read that proper component. For 
instance:

   type Dev_Status is
      Read_Ready : Boolean; -- Bit 3.
      Write_Ready : Boolean;
      ...
   end record;
   for Dev_Status use record
      Read_Ready at 0 range 3 .. 3; -- Bit 3.
      Write_Ready at 0 range 4 .. 4;
      ...
   end record;

   My_Dev_Status : Dev_Status
      with Address => <something appropriate>;

    if My_Dev_Status.Read_Ready then -- Testing bit 3.

QED. :-)

                              Randy.