Regular Expression Animator

Enter a regular expression and input string, click restart, then step:

Regular Expression:
Input String:

Red letter(s) in the regular expression show what part(s) of the pattern will test the next character in the input string:

Red letter in the input string shows which character is about to be tested:

In case you're interested in the state transition table:

Notes:

Tell me more about the red letters in the regular expression.
There are six special regular expression characters: +*?|(). What do they do?
Non-special characters are lower-case "a" through "z". Nothing else is allowed.
So what matched?
Is this an NFA or a DFA?

An additional note (May 2014):

I wrote the Java version of this millions of years ago, when dinosaurs ruled the earth, and Java first came out. In the ensuing millenia, the source code got lost, and the compiled code quit working. So I rewrote it in Javascript.

Comments to doug[at]DougAndJean[dot]com
Back to DougAndJean.com