If other software developers cannot make sense of an engineer's source code, then the code effectively does not contain any of the other metrics discussed here. The qualities may be there in some technical sense, but their impenetrability makes them nonexistent for practical purposes. But if no human can find the single section of source code that relates to a certain feature, no one will be able to fix bugs there or extend the feature in any way. Simplicity Software should do its work and solve its problems in the simplest manner possible. In many ways, simplicity is the most important principle of all and overlaps with all the other principles.
Simple software is beautiful.
Beautiful software is simple. Simple programs are dramatically less expensive to create and maintain, for all of the above reasons. The simplicity of software also is a key metric distinguishing programming ability. Junior programmers create simple solutions to simple problems. Senior programmers create complex solutions to complex problems.