I need a cheap and good software to administrate a restaurant easily and friendly.

NOTE: I want to see on the screen all my tables and can be able to
click in one and add something to its account, and once this happens,
the table change its color and indicates that someone is seated at
this table. One we order the bill, the table changes its color and
indicates this status. And finally manages my inventary, so onece you
add some item to the bill, this item automatically is reduced from the
general inventary.
In the inventory we can add merchandise every day if needed.
And it is important that I can see from another computer

never used it, but i know it  is very widely used: http://www.squirrelsystems.com