PragProg - Orthogonality

Ref: The Pragmatic Programmer

Orthogonality is a term borrowed from geometry. In computing, the term has come to signify a kind of independence or decoupling. Two or more things are orthogonal if changes in one do not affect any of the others.

TIP 13: Eliminate Effects Between Unrelated Things.

Coding

Keep your code decoupled: Write shy code-modules that don't reveal anything unnecessary to other modules and that don't rely on other modules implementations.

Avoid global data: Every time your code references global data, it ties itself into the other components that share that data.