How to make a 2 bit adder?

You can use 555s to make a 2 bit adder but you'll need 20 or more a href="http://hackaday.com/2011/02/28/2-bit-full-adder-using-just-thirty-six-555-timers/" rel="nofollow"http://hackaday.com/2011/02/28/2-bit-ful…/a If you look at the datasheet of the 7483 adder you'll see the complexity using logic gates so it makes sense to use a 7483 if you need a 2 bit adder.