Software entropy

A work on software engineering by Ivar Jacobson et al.[1] describes software entropy as follows:

The second law of thermodynamics, in principle, states that a closed system's disorder cannot be reduced, it can only remain unchanged or increase. A measure of this disorder is entropy. This law also seems plausible for software systems; as a system is modified, its disorder, or entropy, tends to increase. This is known as software entropy.
Within software development, there are similar theories; see Lehman (1985),[2] who suggested a number of laws, of which two were, basically, as follows:
  1. A computer program that is used will be modified
  2. When a program is modified, its complexity will increase, provided that one does not actively work against this.

Andrew Hunt and David Thomas use fixing broken windows as a metaphor for avoiding software entropy in software development.[3]

The process of code refactoring can result in stepwise reductions in software entropy.

Software entropy is increased with accumulation of technical debt.

See also


  1. Jacobson, Ivar; Christerson, Magnus; Jonsson, Patrik; Övergaard, Gunnar (1992), Object-Oriented Software Engineering: A Use Case Driven Approach, ACM Press. Addison–Wesley, pp. 69–70, ISBN 0-201-54435-0
  2. Lehman, M. M.; Belady, L.A. (1985), Program evolution: processes of software change, Academic Press Professional, Inc., San Diego, CA
  3. Hunt, Andrew; Thomas, David (1999), The Pragmatic Programmer, Addison Wesley, ISBN 0-201-61622-X – Item 4 (of 22 tips) is Don't Live with Broken Windows.
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