In Emulators / NES ROMs

Okay, I've been trying to learn how to edit roms. So, I download a rom, and I open it in a text editor. From everything I've read about NES ROMs, they're a system of hexadecimal numbers. Yet, when I open the rom in the form of text, I get a bunch of symbols that look like:

mY®??ÖÙ?@Ö?ÆZLtÅÆZ iÑLtÅ?Z)ù?W)
?? çZ©

if they were hex, you'd have to open them in Hex editor. not just any old text editor.

my question is how would you go about editing a NES ROM in a text editor?!

Yeah, apparently, I don't know nearly as much as I thought. I thought that most games were text which the emulator converted into graphics and such.
In that case, where could I find a hex editor for Mac OSX?

something there is sure to do what you want.

Thanks