What is the font used in the first microsoft logo?

A font is a collection of movable type, either cast in lead or carved in wood. What you are talking about is a typeface, which means the appearance of the letters. You can not copyright a typeface, you can only copyright the name. That is why you see so many identical typefaces with different names. No company is going to pay for a named typeface in their logo. The artist simply draws the typeface he wants while he is drawing everything else.