The Altair 8800

An image of the Altair 8800 with an attached display and keyboard

The Altair 8800 was developed by MITS in 1974 using Intel's 8080 8-bit microprocessor. It was the first commercially successful personal-use computer.
The Altair was a complicated system that required the user to program the system from scratch using the switches. It was compatible
with the S-100 bus, meaning expansion cards could be used with it to increase its computational capabilities.

It was advertised in the Popular Electronics magazine in January 1975,  where Bill Gates and Paul Allen read about it 
and were inspired to make an interpreter for the Altair. 
  

Altair Basic and Microsoft

 Bill Gates and Paul Allen realized the profitability of selling software for computer systems by making computers more 
accessible to the average "computer nerd." So together they made an interpreter that used the BASIC programming language.

Gates and Allen managed to show it off to MITS, who agreed to distribute the Alair with the BASIC interpreter as "Altair BASIC."
The Altair BASIC interpreter was a roll of tape that would be fed into the machine.

Thanks to their success, Gates and Allen founded Micro-Soft in 1975, and soon their MICROSOFT BASIC interpreter would be
ported into thousands of computers and would give a foundation for computer graphic systems during the 80s.