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ygfperson
01-17-2002, 09:38 PM
i read somewhere that computers add using some combination of logic gates, and that the only way multiplication could be done is through addition. is this true, and if so, how?
ty in advance :p

starX
01-17-2002, 11:55 PM
think of multiplication like this:

9 multiplied by 8 means 9 eight times over,
so 9 * 8 == 9+9+9+9+9+9+9+9.

starX
www.axisoftime.com

Deckard
01-18-2002, 06:50 AM
I believe you're thinking of boolean logic gates. You may be interested in the explination provided here (http://www.howstuffworks.com/boolean.htm).

ygfperson
01-18-2002, 09:54 AM
about multiplication: what if the number were big? back when i had a tandy 1000ex(8.077 mhz, 1984 i think) basic could do a for i=1 to 5000, next loop in one second. is there some sort of help the processor gets?

Salem
01-18-2002, 12:58 PM
Well the most common? technique is software is using shift-and-add
http://www.google.com/search?hl=en&q=shift+add+multiply

There is also this
http://www.google.com/search?hl=en&q=booths+algorithm

And perhaps this
http://www.chipcenter.com/circuitcellar/december00/c1200db11.htm

iain
01-18-2002, 01:00 PM
the multiplication cannot actually be done by a computer due to the logic systems it uses, so the multipolication is carried out by bit-shifting and addition

QuestionC
01-18-2002, 08:56 PM
Well, multiplication and loops are different beasts.

For multiplication: Technically, you could just have a multiplication table in your CPU, but the way I learned it, it's a combination of shifts, additions, and perhaps subtractions.

For loops: You can think of increment or decrement operators as even more basic than addition and subtraction. Loops are very important, so much that loop commands are commonly a part of a processor's architecture.

sean
01-18-2002, 10:16 PM
or you may be interested in wasting your time clicking the link provided here (http://www.google.com)

Deckard
01-19-2002, 07:53 AM
Originally posted by Sean
or you may be interested in wasting your time clicking the link provided here (http://www.google.com) That is a stroke of pure genius which should be prominently displayed at the beginning of the FAQ. :)