On Nov 12, 2012, at 14:21 , Ruby Student <ruby.student / gmail.com> wrote:

> I have two large files, about 16 million records each.
> The files are sorted.
> The first 13 characters are used as a key.
> We get an updated file every week.
> We also keep the previous week file.

You or someone else posted this exact problem just a few weeks ago. =
Please don't repost if that was you. Please don't post your homework =
regardless. We're happy to answer questions and give advice. We're not =
happy to directly contribute to your grade.=