It's not that you can't solve the halting problem--- it's that you can't always solve the halting problem. Sometimes (such as when you're building things that c

It's not that you can't solve the halting problem--- it's that you can't always solve the halting problem. Sometimes (such as when you're building things that can explode or kill people) you'll settle for an overly conservative approximation to the halting problem (see http://en.wikipedia.org/wiki/Termination_analysis http://en.wikipedia.org/wiki/Termination_analysis). You'll reject some programs which are OK but anything which passes your analysis will be guaranteed to halt.