"An analysis accomplished after the Challenger accident showed that the IBM-developed PASS software had a latent defect rate of just 0.11 errors per 1,000 lines

"An analysis accomplished after the Challenger accident showed that the IBM-developed PASS software had a latent defect rate of just 0.11 errors per 1,000 lines of code—for all intents and purposes, it was considered error-free. But this remarkable achievement did not come easily or cheap. In an industry where the average line of code cost the government (at the time of the report) approximately $50 (written, documented, and tested), the Primary Avionics System Software cost NASA slightly over $1,000 per line." https://history.nasa.gov/sts1/pages/computer.html https://history.nasa.gov/sts1/pages/computer.html I should really link to this article as well: http://www.ganssle.com/tem/tem400.html#article2 http://www.ganssle.com/tem/tem400.html#article2