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From: gisle@lunde.ii.uib.no (Gisle S�lensminde)
Subject: Re: Why should hackers love Ada. (Re: Ada 95 based RTOS)
Date: 2000/02/24
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Date: 2000-02-24T00:00:00+00:00
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In article <38B47521.1A80B6A1@lmtas.lmco.com>, Gary wrote:
>Hi,
>
>"Marin D. Condic" wrote:
>
>> Ehud Lamm wrote:
>> >
>> In some ways, you'd think "hackers" should be fascinated with Ada. It
>> provides all sorts of facilities to do bit-twiddling and low level
>> access to the hardware.
>
>I see this reference to ADA being good at bit twiddling, periodically.
>Virtually all high-level languages provide facilities for bit twiddling.  Is
>there something unique about ADA (I'm a non-ADA programmers, sorry).  Is this
>a reference to a transfer function (other languages have this) or memory
>aliasing tricks?
>

Because Ada heve some good methods for lowlevel access to hardware, and
this includes bit twidling. Some bit operations are:   

- Bitwise logical operators for modular types, and in the package interfaces 
  there is operators for bitwise shift and rotatate.

- Packed arrays of boolean(and other types). Yoy can declare an array of
  booleans, where each element corresponds to one bit. A 32-bit array of
  packed booleans fits in one word on a 32-bit computer.

- The compiler knows whether the target is a big endian or a little endian
  architecture, and you have tests to find it out, which can be used in code
  to make it portible.

- Representation clauses in records, so you can control where
  "the bits goes" in a record.
  

--
Gisle S�lensminde ( gisle@ii.uib.no )   

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