The $20 Million Bug In Spring 1993, in the Operating System development group at SunSoft, we had a "priority one" bug report come in describing a problem in the asynchronous I/O library. The bug was holding up the sale of $20 million worth of hardware to a customer who specifically needed the library functionality, so we were extremely motivated to find it. After some intensive debugging sessions, the problem was finally traced to a statement that read: x==2; It was a typo for what was intended to be an assignment statement. The programmer 's finger had bounced on the "equals" key, accidentally pressing it twice instead of once. The statement as written compared x to 2, generated true or false, and discarded the result.