Changing chars at specific coordinates w/o reprinting everything

[InDustWeTrust]

How to, instead of reprinting a whole chess board for exemple, changes only the char at given coordinates?

For exemple, how to move the 'o' down here one step to the left, without having the reprint the whole thing?

_________
|xxxxxxx|
|xxoxxxx|
|xxxxxxx|
|xxxxxxx|
---------

My last project was a sudoku, and I had the sudoku being fully reprinted everytime a number was added!