Roberts had hoped for first-year sales to total 200 kits, at $397 each, to break even. When Popular Electronics hit newsstands, 1,000 orders flew in that first month, much to the inventors’ astonishment.

“There was a two-to-three months’ crash project before we developed the final design,” says Zaller, who came back to MITS after the Altair was introduced and recalled that orders began piling up.

Technology aficionados around the country, including two young men in Boston, read the magazine article zealously. This opportunity was precisely what they had been waiting for. Paul Allen, 22 years old and a college dropout working as a Honeywell programmer, and 19-year-old Harvard student Bill Gates, hungered to be a part of this thrilling new chapter of technological history. A few years earlier, in 1971, they had created Traf-O-Data, an electronic data-collection device designed to provide traffic-flow information. Although ultimately unsuccessful, it gave them valuable experience that they could transfer to the Altair, affording them an advantage over others hoping to enter the field quickly.

Another advantage Allen and Gates wielded was their chutzpah. Without solicitation, they telephoned Roberts exclaiming that they had a program that would work on his Altair. Roberts knew the machine was impractical without a way for buyers to put it to use, so he urged them to come to Albuquerque. Working practically nonstop for a few months, Allen and Gates wrote BASIC — Beginner’s All-purpose Symbolic Instruction Code, an uncomplicated programming language allowing users to program their computers — for the Altair.

Upon completion of the code, Allen flew to Albuquerque, armed with a roll of paper tape recording the BASIC he and Gates had developed.

The Altair’s first task was to add 2 + 2.

Allen held his breath as the machine crunched out the answer: 4.

This equation was indeed part of the first successful program written for a personal computer. Roberts was ecstatic, and Allen was relieved.
“Ed wasn’t as surprised as I was that our … BASIC had run perfectly its first time out of the chute,” Allen wrote in his 2011 autobiography, Idea Man.

With this milestone, the age of the personal computer had officially dawned. “The invention of personal computers and software changed the world; it’s up there with the discovery of the wheel and fire,” says Spencer Lucas, chief curator of the New Mexico Museum of Natural History and Science.