Lines of code

Program sizes are sometimes measured in the number of lines of source code, usually expressed as Thousands of Lines Of Code or KLOC (pronounced KAY-lock). An interesting article about this at Discovery News:

This Car Runs on Code
The Toyota recall may be a harbinger of things to come in the auto industry, where vehicle electronics are getting more and more complex.

The avionics system in the F-22 Raptor, the current U.S. Air Force frontline jet fighter, consists of about 1.7 million lines of software code. The F-35 Joint Strike Fighter, scheduled to become operational in 2010, will require about 5.7 million lines of code to operate its onboard systems. And Boeing�s new 787 Dreamliner, scheduled to be delivered to customers in 2010, requires about 6.5 million lines of software code to operate its avionics and onboard support systems.

These are impressive amounts of software, yet if you bought a premium-class automobile recently, �it probably contains close to 100 million lines of software code,� says Manfred Broy, a professor of informatics at Technical University, Munich, and a leading expert on software in cars. All that software executes on 70 to 100 microprocessor-based electronic control units (ECUs) networked throughout the body of your car.

The article goes on to cite examples of bad software, the fact that the parts cannot be repaired -- only replaced and that the quantity of computing makes the car difficult to diagnose. A bad trend in my book -- OK if you want a luxury vehicle and live near a dealership but not something for ruggedness and utility in the country. If a sensor goes out, I want to still be able to drive. This is, in part, why the mission-critical vehicles like passenger planes have so little actual computing power.