Many people heard that all cars produced for last 20 years using “chips” or processors to control different operations of car. So basically, it is small computer that for example calculate proportion of air in petrol for engine based on current speed, quality of petrol etc.  And all computers require software, and this is program computer executes. Technically it can be done in hardware, but it is quite expensive to product custom chip for every operation and quite expensive to change. So, using general processor is much more effective.

And as everyone knows any program may have mistakes (they called bugs in software industry). Of course, probability that simple program has bug is quite low. But the more complex program