Linus Torvalds use of assembly language. After the VIC-20 he purchased a Sinclair QL, which he modified extensively, especially its operating system. "Because it was so hard to get software for it in Finland, Linus wrote his own assembler and editor (in addition to Pac-Man graphics libraries)" for the QL, as well as a few games. He wrote a "Pac-Man" clone named "Cool Man". On January 5, 1991 he purchased an Intel 80386-based clone of IBM PC before receiving his MINIX copy, which in turn enabled him to begin work on Linux. The first prototypes of Linux were publicly released later that
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