Plankalkül

Zuse wrote an autobiography, and it has been translated into English -- https://www.amazon.ca/Computer-My-Life-Konrad-Zuse/dp/354056...

Chapter 5 - Origins of the Z4 - News from the United States - Attempt at a Ph. D. dissertation - Computing machine for logic operations - Final months of the war in Berlin - The evacuation - Z4 completed in Göttingen - Final war days in the Allgäu

Early in the war, he got drafted into the army and got a release for his technical work. By the end of the war, he was working on the Z4 to assist calculations for war work at a lab in Berlin. In early 1945, his labs and work were heavily damaged by bombing, some of the machines destroyed. He packaged up what remained physically and shipped it by rail to a town to the southeast. He resumed work there for a few weeks. He then they fled, as many other groups did at this time, to the very south in German-controlled territory that would become part of the American sector. He does write a bit about that period:

> Dr. Funk obtained the necessary papers for me, my wife and all my assistants to get out of Berlin. Only a few chose to stay. It was painful for me to leave my parents behind in Berlin. They had supported me all those years. I was able to take the most important papers with me. But what was important? With hindsight I would have known better. On this occasion, too, much of value was lost.

> In Gottingen, a relative calm filled the weeks that followed. The Z4 was assembled in the Aerodynamischer Versuchanstalt. We were able to get it running so well that it executed the first program-controlled calculations. While we demonstrated for the gentlemen of the Aerodynamischer Versuchanstalt, including the famous Professors Prandtl and Kuessner -- we could aready hear the thunder of the cannons in Kassel. today we know that we could have been overrun in Gottingen, but at the time no one could have known what would happen. Gottingen could have become a theater of the war, for it was not far from the great underground ordinance factories in the Harz region. Later, Gottingen was occupied by the British. They definitely would have been very interested in the Z4. And we could have been sent to England along with our machine. But this was not to be.

> The Z4 was our first priority. Finally we got the "order" to deliver it to one of the underground ordinance factories. The visit there was for us - we were completely accustomed to the Berlin bombings - deeply shocking. For the first time we stood face to face with the inhuman atrocities of the Third Reich. Twenty thousand concentration camp prisoners worked under unimaginable conditions in kilometre-long tunnels. During the retreat from the East, far too many prisoners were assembled together here, and no provisions had been made to assure that there would be enough food for them. After the visit we told ourselves, "Anywhere, but not here!" We asked them for just one Wehrmacht truck and trailer with which to transport the device.

> Around the same time Wernher von Braun's team was moved from the Harz to Bavaria; and through General Dornberger we were able to get our marching orders for Bavaria, along with a thousand liters of diesel fuel. For fourteen days we fled along the front, past burning neighborhoods and over bombed-out streets. We usually drove at night; during the day we found makeshift shelter with the farmers. [...]

> The night drive through Munich was really eerie: the streets were deserted, the city veiled in darkness, air raids were expected. But nothing happened this night. There was a ghostly silence. We drove straight through and did not stop until we reached the Alps. For the first time in my life, I saw the high mountain region. How peaceful the cloister of Ettal seemed. But we had to push on. In Oberjoch bei Hindelang we finally found temporary quarters, which we shared with Wernher von Braun and his assistants.

https://en.m.wikipedia.org/wiki/Calculating_Space

From my understanding the way his ideas surrounding computer design developed was dependent on the limitations of German resources during the war. As such Zuse was focused on mechanical designs while others in the rest of the world focused more on electromechanical dominated designs.

The end result is that Zuse spent a lot of time going in different directions after the war, developing things that seemed to be curiosities at the time but may end up being critical in space exploration.

https://www.youtube.com/watch?v=odwgpKRnWM8

https://www.iaarc.org/publications/proceedings_of_the_27th_i...

http://zuse.zib.de/assemblyLineSelfReplicatingSystems

I guess by that time it was hard to catch up. Also, many of our scientists had left for the US during the war.

Population of Germany:

  - 1940: 70 million
  - 2020: 83 million (about 20% more)

  - 1940: 132 million
  - 2020: 331 million (about 140% more)

  - 1940: 2300 million
  - 2020: 7795 million (about 240% more)

An example of this to me is Dickmann's autonomous cars which were driving around on highways in the 80s (https://youtu.be/_HbVWm7wdmE), yet you'd hardly think they even existed given how the rate of progress is framed in that industry by consumer products.

Even if Germany's brightest were not brain-drained to USA/USSR, they would not have much funding nor opportunity to pursue their advanced research in occupied Germany.

...this bit of information was actually news to me, but the brain drain that started in 1933 and then intensified after WW2 is probably an important part of the answer. Maybe it also contributed to a general mindset that the grass is greener across the ocean ;)

A lot of innovation still happened in Germany after the war - even in East Germany, but somehow the fruits were always picked elsewhere, for example: https://www.youtube.com/watch?v=1qccejmqbPg - or this 'German SpaceX': https://en.wikipedia.org/wiki/OTRAG)

The later languages were much more constrained by actual implementations.

On the other hand the later implementors realized that some convenience is needed, for example even the earliest languages (like autocode) had variable names instead of variable numbers.

> Plankalkül was more comprehensively published [vague] in 1972. The first compiler was implemented by Joachim Hohmann in his 1975 dissertation. Other independent implementations followed in 1998 and 2000 at the Free University of Berlin.

So it was never implemented until mid-1970s, which likely made its design process less constrained than languages that came soon after it in 1950s etc.

Recursion can actually be a pit fall if you parse user generated data and don't set recursion limits. If feasible I try to avoid recursion.

Edit: if it somehow supports passing functions (or function pointers) as parameters, the Y combinator can be used to add recursion even if it's not natively supported otherwise.