Unix philosophy
The Unix philosophy, originated by Ken Thompson, is a set of cultural norms and philosophical approaches to minimalist, modular software development. It is based on the experience of leading developers of the Unix operating system. Early Unix developers were important in bringing the concepts of modularity and reusability into software engineering practice, spawning a “software tools” movement. Over time, the leading developers of Unix (and programs that ran on it) established a set of cultural norms for developing software; these norms became as important and influential as the technology of Unix itself; this has been termed the “Unix philosophy.”
The Unix philosophy emphasizes building simple, short, clear, modular, and extensible code that can be easily maintained and repurposed by developers other than its creators. The Unix philosophy favors composability as opposed to monolithic design.
Do One Thing and Do It Well
As stated by McIlroy, and generally accepted throughout the Unix community, Unix programs have always been expected to follow the concept of DOTADIW, or “Do One Thing And Do It Well.” There are limited sources for the acronym DOTADIW on the Internet, but it is discussed at length during the development and packaging of new operating systems, especially in the Linux community.
Patrick Volkerding, the project lead of Slackware Linux, invoked this design principle in a criticism of the systemd architecture, stating that, “attempting to control services, sockets, devices, mounts, etc., all within one daemon flies in the face of the Unix concept of doing one thing and doing it well.”
KISS principle
KISS, an acronym for keep it simple, stupid, is a design principle noted by the U.S. Navy in 1960. The KISS principle states that most systems work best if they are kept simple rather than made complicated; therefore, simplicity should be a key goal in design, and unnecessary complexity should be avoided. The phrase has been associated with aircraft engineer Kelly Johnson.