Google is taking its search expertise to one of its favorite audiences: software developers.

The company on Thursday is expected to launch a Web site, Google Code Search, which the company says will let programmers search billions of lines of code.

The service, conceived by the Google Labs early technology group, will crawl publicly available code, most of which is made available through open-source projects. The search and indexing can cover code on Web pages as well as code that resides in compressed files, said Tom Stocky, a product manager at Google.

Google expects that the search engine will be used primarily as a learning tool to help students and serious programmers, rather than a way to find and copy another person's code.

"Most of the code is open source so you can reuse it. But I don't think that's the primary use--it's more about how to learn about things and, when you're building open-source packages, to make sure you doing it the right way," Stocky said.