finding more code space in an exe

what i am about to say could be completely wrong or make no sense, because i dont really have any clue about most of what you guys talk about lol.

but is it possible to open the file up as binary, then append to the file the code you want.

would that work so that you could put the extra code you need into the program.

oh yeah i havent even got a clue how to do what i just said even though apparently it is quite simple, i just read it somewhere, dont remember where.