Topic summary
Version number
Extracted from the Wikipedia article Software versioning.
TeX
TeX has an idiosyncratic version numbering system, an unusual feature invented by its developer Donald Knuth. Since version 3.1, updates have been indicated by adding an extra digit at the end, so that the version number asymptotically approaches the number π, so 3.14 effectively means 3.2 in semantic versioning. (This is a form of unary numbering; the version number is the number of digits.) Since 2021, the version number has been 3.141592653. This is a reflection of TeX being very stable, and only minor updates are anticipated. TeX developer Donald Knuth has stated that the "absolutely final change (to be made after [his] death)" will be to change the version number to π, at which point all remaining bugs will become permanent features.