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 ROM and known as "monitors". One notable early disk operating system was CP/M, which was supported on many early microcomputers and was closely imitated by Microsoft's MS-DOS, which became widely popular as the operating system chosen for the IBM PC (IBM's version of it was called IBM DOS or PC DOS). In the 1980s, Apple Computer Inc. (now Apple Inc.) abandoned its popular Apple II series of microcomputers to introduce the Apple Macintosh computer with an innovative graphical user interface (GUI) to the Mac OS. The introduction of the Intel 80386 CPU chip in October 1985, with 32-bit architecture and