Linux kernel an SCM system which satisfied Torvalds' technical requirements. BitKeeper was made available to Linus and several others free of charge but was not free software, which was a source of controversy. The system did provide some interoperability with free SCM systems such as CVS and Subversion. In April 2005, efforts to reverse-engineer the BitKeeper system by Andrew Tridgell led BitMover, the company which maintained BitKeeper, to stop supporting the Linux development community. In response, Torvalds and others wrote a new source code control system for the purpose, called Git. The new system was written within weeks, and in two months
Operating system existing hardware production. MCP is still in use today in the Unisys ClearPath/MCP line of computers. UNIVAC, the first commercial computer manufacturer, produced a series of EXEC operating systems. Like all early main-frame systems, this batch-oriented system managed magnetic drums, disks, card readers and line printers. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the Dartmouth BC system. General Electric and MIT developed General Electric Comprehensive Operating Supervisor (GECOS), which introduced the concept of ringed security privilege levels. After acquisition by Honeywell it was renamed General Comprehensive Operating System (GCOS).