At Microsoft Future Decoded, we demonstrated how Microsoft’s future could decode its past

Our challenge demonstrated how a Microsoft Hololens, as a mixed-reality device which can enable extremely rich collaboration between on-the-ground callers and remote experts, can enable delegates to flip binary switches and interpret the blinking LEDs of a replica 1975-era Altair 8800, in its most basic configuration and without any keyboards or monitors.

The challenge illustrated how the extraordinary capabilities of the Hololens can provide rich and remote guidance with annotation and 3D collaboration to benefit from the expertise of someone remotely – and how this allows the remote help to ‘borrow the eyes’ of the user requesting assistance.


Is it history? The box used in the challenge is not a genuine 43-year old Altair 8800. Authentic machines are now very rare, expensive and fragile. It is, in fact, a modern replica produced by BJSS Software Engineer, Bob Stone.

Under the hood, the machine is powered by an Arduino Dué. Bob has built several such solder kits, most recently a DEC PDP-11/70, which was the original UNIX workhorse of the 1970s. He has also built a replica of the Apollo Guidance Computer – the machine used nearly fifty years ago to help man land on the moon.

In this article about the history of the Altair 8800 and the creation of Microsoft, Bob discusses his interest in vintage computers. Bob likes to think of his interest in these recreations – along with learning to use them and absorbing the historical anecdotes that swirled around them – as being like a Druid of the early computer era, keeping the ‘old ways’ alive – lest they fall into myth! But, given that they’re modern replicas, Bob guesses that in truth he really enjoys LARPing in binary!

Bob Stone

Bob Stone

The box used in the challenge is not a genuine 43-year old Altair 8800.

Authentic machines are now very rare, expensive and fragile.

It is, in fact, a modern replica produced by BJSS Software Engineer, Bob Stone.


The first time I ever touched a computer was 1980. It was a Sinclair ZX80 which my dad, an engineer in a power station, brought home. This experimental purchase had been made by the efficiency department at his power station. They wanted to see if these new-fangled home computers could be leveraged to bring multi-part computed calculations into their own domain, control and budget instead of relying on the arrogant wizards who guarded the timeshared, punched-card driven mainframes.

The second computer I encountered was a Tandy TRS-80. While this machine was slightly older – very typical of the late-70s US computing scene – it was more capable than the ZX80 and had its own monitor too. I was ten years old at the time, and I spent the summer with my friend learning how they worked, and then teaching my dad to write engineering calculations in BASIC.

This is not the story, but it sets the scene for my long-time interest in vintage computers – from the ZX81 that I was given in 1981 for my birthday, to machines even older than the era of home computing, and then to those semi-mythological computers that I read about in the magazines from the Middle Earth of computing.

Instead, this story is about the beginnings of home computing.

It is tricky to pin down precisely when that beginning was. But one popularly cited candidate of an affordable home computer would be the Altair 8800. It was the brainchild of Ed Roberts, founder and owner of Micro Instrumentation and Telemetry Systems, or MITS. Roberts bet that the rise of very early microprocessors like the Intel 4004 (only a 4-bit processor) would enable him to sell ‘build it yourself’ desktop calculator kits that were more affordable than other machines at the time. He was right, but it was a short-lived success, because bigger players like Commodore quickly churned out fully-built pocket calculators, making the MITS kits irrelevant.

But then the editor of Popular Electronics magazine, contacted Roberts with a request. Competing magazines had started to use serialised articles which would, over time, enable the reader to build a computer. They wanted Ed to counter with a better one, hoping his calculator kit experience would make the difference. What had made it possible of course was the early microprocessors, and this rival magazine’s computer design was based on Intel’s follow-up, the 8008. But it was still a calculator chip at heart. Roberts agreed to make a computer design Popular Electronics could serialise, but on condition that they used Intel’s forthcoming 8080 chip instead, more powerful than the 8008.

Later, when the prototype was delivered, Popular Electronics published their article. It piqued the interest of Paul Allen (RIP), who showed it to his friend, Bill Gates. Gates had written a BASIC interpreter for Digital Equipment Corp’s PDP-10 mainframe at Harvard, and Allen persuaded Gates to port it to the Altair and create the first high-level language for the first home-affordable computer.

Gates called Ed Roberts and claimed that he and his friend were part way through working on a BASIC interpreter running on his Intel 8080-based Altair machine, and would like to discuss licensing it as an official language for the Altair. Of course, Gates and Allen didn’t have an Altair, or even access to an Intel 8080 processor, and Roberts knew they were bluffing – and he decided to call that bluff! The three agreed to a demo eight weeks later.

Without a real Altair, Allen wrote a translation layer between the Intel 8080 assembly language and the DEC PDP-10s which enabled Gates to port his BASIC to 8080 machine code and run it (slowly) transcribing into PDP-10 code. Gates then spent the eight weeks at Harvard eschewing his studies entirely, using University resources full time to port BASIC to Altair machine code.

While Gates and Allen still hadn’t seen a real Altair in the flesh, they managed to get a demonstrable, if not entirely feature-complete, version up and running – at least on the DEC computers. They met the challenging deadline.

It was only while they were in the air, flying to demo to Roberts, did the pair realise they they were loading the BASIC implementation from a paper tape, and that it would run on a machine with no ROM that couldn’t speak to the paper tape reader. Fortunately, at least some of the instructions for how to read from paper tape could be read… from paper tape!  If they toggled in a ‘rim’ loader, the key instructions to turn the reader motor on and execute whatever comes in through it. Allen quickly wrote a rim loader before landing.

It didn’t work! This was the first time that the code had been tried on the real hardware, and it was also the first time that Allen’s bootloader had ever been run. But it turned out to be just a miskeying, the loader was sound, and on the second try the paper tape reader clattered into life to load up their 4k BASIC.

Roberts was more than impressed, he signed to license it as the official Altair BASIC, offered discounts on the necessary hardware upgrades to purchasers, and this really set the scene for a home computer much more capable than its own designer had really foreseen. Allen became MITS’ Head of Software, but separately, he and Gates started a company called Micro-Soft, which offered their BASIC interpreter as their first product.