Ey up!

Currently underway with a college project - i've got to create a game of hangman. I've done every part except this last bit. I don't want to know how to do the game, or anything like that.. all i would like to know, is how i could replace a character within a string, at a position, with another.

For example, if i had "_ _ _ _" (without spaces) how could i replace ONLY the second letter with say an "E"...or a letter stored in a variable ?

Cheers!