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 device drivers to the operating system's kernel, where they can be passed onto applications, or carried out directly. Security of operating systems has long been a concern because of highly sensitive data held on computers, both of a commercial and military nature. The United States Government Department of Defense (DoD) created the "Trusted Computer System Evaluation Criteria" (TCSEC) which is a standard that sets basic requirements for assessing the effectiveness of security. This became of vital importance to operating system makers, because the TCSEC was used to evaluate, classify and select trusted operating systems being considered for the processing, storage