(Meanwhile, apparently MS itself continued using SLM, the in-house source-control system which had been commercialised as MS Delta, internally until about 2000. https://wiki.c2.com/?MicrosoftDelta https://devblogs.microsoft.com/oldnewthing/20180122-00/?p=97... https://ricomariani.medium.com/super-brief-notes-on-early-so... https://news.ycombinator.com/item?id=44255526 )