Lex and Yacc

Hello,
I have a class where I'm supposed to create a program for lex and then one for yacc which on my school olympus account is flex and bison. I was wondering how do I go about creating editing the files? Can I use flex and bison to create and edit them or are they just for running the programs. I've been looking around online and cannot seem to find any information on it. Should I try to use something like the VI editor or is there a way to use the other two commands to start on the programs?

Input files to lex and yacc are regular text files just like C programs are, so any text editor will do.
As for the syntax etc of the contents of these files, well that's a whole different ball game

Alright thanks. I tried using VI editor but it seemed so complicated and then just found pico. Seems a lot easier. Thanks though. :)