Why do we program computers?

Think of when you first programmed, whether it was a Basic program that greeted you by name or a spreadsheet macro.  Do you remember the thrill of running that program and seeing it produce output?

In those days, it was probably rewarding enough that the program responded at all.  Even better if the output looked reasonably correct.  Unless we're programming for out own amusement, though, we must move beyond that starting point.

We program because '''we want the computer to do something for us'''.  We may want to automate a repetitive task, to perform some long, time-consuming calculation, or to enhance our abilities across time and distance.

''This implies that we should write our program such that the computer understands it.  Mostly, this is a matter of using the syntax of the chosen computer language correctly.  We also need to convert the program from the form we use for writing to the form installed on the computer.''

We program because '''we want the correct answer'''.  Sure, in some cases there may be discussion on ''how correct'' or ''close enough,'' but we certainly don't want it to be wrong.

''This implies that we should should verify the correctness of our program.  We may use proofs or inspections for verifications, and we should test important cases to verify the desired behavior.  Verification by testing is so important, that the tests should be automated so they may easily be re-run.  We should write our programs to make them testable.''

We program because, in spite of all the programs that have been previously written, '''we always seem to want one more thing,''' one more bit of functionality, or combination of existing functionalities, or presentation of functionality, than we already have.  It's a never-ending quest, and will be so for as long as there are people.

''This implies that we should write our programs for clarity, so that future programmers (including ourselves) may understand what we've already done.  We should implement functionality without duplication, so that when we want to change that functionality, we can be sure it operates consistently.''