How did Microsoft manage to achieve a monopoly on the market for operating systems?

Peter S: How did Microsoft manage to achieve a monopoly on the market for operating systems?
Microsoft was founded in 1975 and Apple was founded in 1976, which is just one year later. Then how did Microsoft manage to achieve over 80% of the market share and Apple only about 5-10%?

Answers and Views:

Answer by Common Sense
80% is not a monopoly. The reason is Apple refused to license their hardware and software to other manufacturers to keep the price high.

Answer by rtfm
You should probably check the definition of the word “monopoly”.

Answer by bbqmon
Because Microsoft did it right and knows what they’re doing and Apple is an overpriced POS.