Linus Torvalds Second Lieutenant, with the role of a ballistic calculation officer. Torvalds bought computer science professor Andrew Tanenbaum's book "", in which Tanenbaum describes MINIX, an educational stripped-down version of Unix. In 1990, he resumed his university studies, and was exposed to UNIX for the first time, in the form of a DEC MicroVAX running ULTRIX. His M.Sc. thesis was titled "Linux: A Portable Operating System". His interest in computers began with a Commodore VIC-20, at the age of 11 in 1981, initially programming in BASIC, but later by directly accessing the 6502 CPU in machine code. He did not make
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).