[RC5] Eh?

Skip Huffman SHuffman at Atl.Carreker.Com
Tue Nov 10 07:58:45 EST 1998


On Mon, 9 Nov 1998 18:22:58 -0600 (CST), root at barnstormers.dyn.ml.org
wrote:

>well, I can tell you this, FIFO stands for First In First Out.  It means
>in buffers that the first block that goes in, is the first to be
>processed.  LIFO is the opposite. LIFO stands for Last In First Out.  That
>means the last block you put on is out first.  I can't think of any good
>examples of this.  If I'm wrong please let me know, but I think that's it.


First In First Out is sometimes also called queueing.  Basically the
oldest item in a group is removed first.  It is the way you hope your
grocer stocks his shelves.  Put the new stuff at the back so that the
older stuff is pushed to the front of the shelf and gets picked up.
That way the stuff on the back of the shelf does not sit there for
ages.

Last In First Out is sometimes called stacking.  Basically the most
recently added item to a group is used first.  It is the way your
hardware store stocks nuts and bolts.  The newest stuff just gets
dumped on top of the older stuff and so gets purchased first., This
does not matter because steel does not spoil terribly quickly; a new
bolt is no better than an old one.

FIFO is slower and requires more effort, both in real life and for
computer programs.  When your grocer stocks oranges, he has to take
all the remaining oranges off the shelf, put the new ones there, then
put the old ones on top.  

LIFO is faster and requires less effort.  When your hardware man gets
notices the 10mm nuts are getting low, he just dumps some more on
top.  No need to empty the bin first.

Computer data works simularly, but involves the hairy-scairy details
of pointers, memory addresses, allocations, and such.

I hope this helps on the one example.
--
Skip Huffman, Carreker-Antinori
Atlanta Office, Quality Group    

You know that you are drinking too much coffee if:
... You have a conniption over spilled milk.


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