Is it possible for two arduino Uno to communicate? because I am currently lacking in Input/output pins in my design, I'm thinking that i can use another arduino Uno so that i can have more i/o pins but is it even possible? if yes, how it is done? or should i buy another arduino board that has more I/O pins than arduino UNO? 
Please do not cross-post.
Yes: connect Rx to Tx, Tx to Rx, Gnd to Gnd.
May also use software serial.
May also SPI.
May also use I2C
May also use '1284P design with 32 IO.
Kits available:
http://www.crossroadsfencing.com/BobuinoRev17
Or go with two '328Ps on a board:
Boards available:
Or depending on the IO, add a bunch of shift-out registers:
Or go the Mega route. Lots of options.
Coding Badly,
You took care of the crosspost? I did not see a duplicate post to delete and/or merge.
CrossRoads:
You took care of the crosspost?
Yes.
I did not see a duplicate post to delete and/or merge.
Edited the other message to just include the "thank you".
im sorry for the cross post. anyway thanks for the answer
If we knew more about your design we may be able to suggest ways to utilize the pins on one Uno to do the job (shift regesters, I2C expanders).