A number of great historical moments took place in 1975. South Vietnam fell, Muhammad Ali defeated Joe Frazier in the 'Thrilla in Manila' world championship boxing match, One Flew Over the Cuckoo's Nest swept the boards at the Oscars, and Glenn Campbell's 'Rhinestone Cowboy' topped the music charts.
We look at the company's best, worst and most notable moments
And Harvard dropout Bill Gates and his high school friend Paul Allen set up a tiny business to write software for a new microcomputer called the Altair 8800.
Their first product is the Altair BASIC language. At some point during that year, the company is called Micro-soft, and then MicroSoft, before it is ultimately named Microsoft.
From those modest beginnings, that company went on to help give birth to an entire industry, change the way we live and work, and become one of the largest software companies on the planet, creating countless millionaires - and several billionaires - along the way.
As Microsoft celebrates its 35th anniversary, I've decided to take an idiosyncratic and opinionated look at the best, worst and most notable moments, technologies, products, decisions and people in the company's history.
So step into our time machine and read on.
Savviest business deal
In November 1980, Microsoft signed an agreement with IBM to provide an operating system for the still-secret IBM Personal Computer, to be released in 1981.
The operating system would ultimately be called PC-DOS, a rebranding of Microsoft's MS-DOS.
Microsoft didn't actually write MS-DOS; instead it paid to have Seattle Computer rewrite its own QDOS (Quick-and-Dirty Operating System) for the purpose, without telling Seattle Computer to whom the operating system would be sold.
(Microsoft signed the contract with Seattle Computer one day after signing the contract with IBM.)
QDOS was largely based on the CP/M operating system, owned by Digital Research.
Ironically, IBM had originally turned to Digital Research for an operating system for the IBM PC, but the two companies' negotiations broke down.
Too bad for Digital Research. Microsoft went on to use its relationship with IBM as a springboard to develop its worldwide dominance in business operating systems.
In July 1987, Microsoft bought Forethought for $14m in cash. Forethought had developed a presentation program for the Macintosh, initially called Presenter, which it renamed PowerPoint for trademark reasons.
PowerPoint later became one of the core programs of Microsoft Office, which for many years has been the dominant office productivity suite.
In August 1985, Microsoft and IBM signed a deal to partner in the development of an advanced operating system called OS/2.
The operating system never achieved the widespread popularity of DOS - or, later on, Windows - and became a bone of contention between Microsoft and IBM.
Microsoft devoted most of its development resources to Windows and Windows NT, rather than OS/2, and ultimately abandoned OS/2 to IBM, which eventually abandoned it as well.
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