System debugging, like astronomy, has always been done chiefly at night.

Even the best planning is not so omniscient as to get it right the first time.

How does a project get to be a year behind schedule? One day at a time.

Software and hardware design is less different than software designers think, but more different than hardware designers think.

A design style is defined by a set of microdecisions. A clear style reflects a consistent set. A clear style may not be a good style; a muddled one never is.

The hardest single part of building a software system is deciding precisely what to build the most important function that software builders do for their clients is the iterative extraction and refinement of the product requirements. For the truth is, the clients do not know what they want. They usually do not know what questions must be answered, and they have almost never thought of the problem in the detail that must be specified.

Systems program building is an entropy-decreasing process, hence inherently metastable. Program maintenance is an entropy-increasing process, and even its most skillful execution only delays the subsidence of the system into unfixable obsolescence.