Software bug

A computer bug is an error that occurs in a computer program. Often these can be detected and "handled", as by Visual Basic's On Error Goto statement or C++ and Java's throw . . . catch syntax.

Programmers generally find it easier to find and fix computer bugs that they can reproduce. Some will refuse to even try to find irreproduceable bugs, as the effort required is often harder by orders of magnitude.

In C++, a common and vexing source of computer bugs is memory addressing. Overrunning the end of an array or accessing an non-existent object can cause hard-to-trace errors. Java does not permit the programmer to address memory directly or to perform address arithmetic, and all array references are checked. Fans of Java maintain that Java is superior to C++ in this respect.

It is considered good programming practice to anticipate possible program errors and write error handlers for them. Unanticipated errors are a prime source of computer bugs.

Computer bugs can be very expensive. Steve McConnell recounts several bugs that cost over $100 million. The Ariane rocket that self-destructed may have cost over $1 billion.