- The original NMOS version of the MOS 6502, used in computers like the Commodore 64, the Apple II and the Nintendo Entertainment System (NES), is well-known for its illegal opcodes: Out of 256 possible opcodes, 151 are defined by the architecture, but many of the remaining 105 undefined opcodes do useful things.
- Aztec philosophy (Wikipedia)
Aztec philosophy was a school of philosophy that developed out of Aztec culture. The Aztecs had a well-developed school of philosophy, perhaps the most developed in the Americas and in many ways comparable to Ancient Greek philosophy, even amassing more texts than the ancient Greeks. Aztec cosmology was in some sense dualistic, but exhibited a less common form of it known as dialectical monism. Aztec philosophy also included ethics and aesthetics. It has been asserted that the central question in Aztec philosophy was how people can find stability and balance in an ephemeral world.