Strong typing

Another nail in the coffin of the weak typist. According to Coding Horror, typing is a core programming discipline. With weak typing skills, a possible recourse might be to use weakly typed languages, or to devote more time to planning before embarking on the next hunting and pecking expedition.

The formula for the amortization schedule payment mentioned in the annual percentage rate wikipedia article is derived in the amortization calculator wikipedia article.

Premature optimization and its relation to evil is discussed in a wikipedia article on optimization. Premature optimization may result in traversing many local extrema that turn out to be unacceptable, before reaching the global extremum (or an acceptable local extremum, or running out of time). What is being optimized is the time to execute a program, while neglecting the time it takes to develop it.

According to Paul Graham, The distinguishing feature of nasty little problems is that you don't learn anything from them. ... Working on nasty little problems makes you stupid. And this, in turn, makes you more qualified to work on more nasty little problems, resulting in an infinite regression.