Re: Looking for Long Tooth...

["Scott P. Smith" <ssmith@scott-smith.com>]

Two more common uses:

* Almost all graphics file formats store a single pixel's RGB values in a 16
or 32 bit value.  To access the components (in order to display the file)
you need bitwise operators.

* High end databases use bitmaps as a way to make indexed searches faster.
I am relatively naive regarding this, so I won't attempt to explain it.

Scott Smith

----- Original Message -----
From: "Scott P. Smith" <ssmith@scott-smith.com>
To: "Atlanta Java Users Group" <ajug-members@ajug.org>
Sent: Wednesday, April 09, 2003 9:31 AM
Subject: Re: Looking for Long Tooth...


> I am a little surprised by this question and the other one like it a few
> weeks ago.  I have a sneaky feeling that I am helping a college student do
> his homework, but I'll respond anyway.
>
> There are infinitely many ways these operators can be useful.. But I'll
just
> give a few examples:
>
> * Data Compression - Many data compression algorithms compress byte
streams
> into bit streams.  To create (and later decode) the bit streams, you need
> bitwise operators.
>
> * Non-Java Binary File I/O - When working with binary files that were
> created in C, C++, etc. you will see a lot of use of things like unsigned
> 16, and 32 bit values. Since Java doesn't support these, you have to use
> bitwise operators to put the uint16 into a Java int32. And vise versa.
>
> * Old file formats - Like the previous example.  A long time ago, (when
> dinosaurs still roamed the earth and when I was in high-school)  people
did
> not have much disk space.  So file formats made HEAVY use of bit fields to
> store a series of boolean flags.  To read or write these flags use need -
> bitwise operators.
>
> * Arbitrarily Precision Integer Math - Math packages that implement 64,
128,
> 256 bit integers, etc.  These packages use bitwise operators (at least I
> think they do).
>
> * Hardware Simulation - Hardware adders multipliers etc. are sometimes
> simulated in software using bitwise operations. Not common, but I did this
> back in School.
>
> Scott Smith
>
>
> ----- Original Message -----
> From: "Lee Chalupa" <lchalupa@seelink.org>
> To: "Atlanta Java Users Group" <ajug-members@ajug.org>
> Sent: Wednesday, April 09, 2003 9:24 AM
> Subject: Looking for Long Tooth...
>
>
> > Hello:
> >
> > I would like to find some examples of business problems that are
addressed
> > using
> > bitwise operators or shift operators.
> >
> > I think one of the reasons people have trouble with these two topics is
> > that they
> > seem irrelevant to their work.
> >
> > My guess is that some of our more experienced programmers used these
> > operators in the "good old days".
> >
> > Does anybody have some practical examples of where they put these
> operators
> > to good use?
> >
> > Thanks
> >
> > Lee Chalupa
> > AJUG Certification Group
> >
> >
>
>