Please help me about my project. I'm supposed to design a full adder/subtractor... it should only have two inputs and another more input for switching between the adder and subtractor. Does anyone here have a schematic diagram for this circuit? I'd really appreciate it if you would help me

 

something like this?
http://www.play-hookey.com/digital/binary_subtraction.html
try a google search for more.

 

It's a lot more fun designing it. Don't shy away from learning logic and state machines, it really isn't that horrific to learn and plenty useful.

Steve

 

thanks for the help... I really wish I could design it...unfortunately i'm already time pressured

 

i alredi design the 4 bit-adder n subtractor..i realy dunnu how to insert switching system there..any1 can help??i really need for fyp...

 

Just use a multiplexer to switch between the addition and subtraction inputs...this wikipedia article helped me out:
http://en.wikipedia.org/wiki/Adder-subtracter