Discovery: User Manual of the Zuse Z4

Also sounds like IEEE 754 forty years before IEEE 754.

Fascinating. From page 8, §11, in the section on "Unterpläne", it looks also as if it used a kind of function calls and subroutines. "Plan" seems to mean "program", so "Unterplan" is literally subprogram, and it had a facility to automatically return to the point where it the subprogram was called.

It may not be obvious to HN'ers who grew up this century, but while some of the images (such as the illustration of film holes for the opcodes, K1.§4) and underlining was done on the typewriter, many of the graphics and special symbols (e.g. K1 hero image, or I/O, K2.§6) would then be added by hand in a second pass, à la MathJax.

Am I reading K4.§1 correctly that intermediate values were kept to about 80 bits?

I am fond of the hack of K3.§5.4. We unroll loops, they rolled them.

Especially important: K5.§1: bugs and workarounds!

I think all of them are important but clearly Konrad Zuse has received way less attention than he deserves. Growing up I remember being taught that ENIAC was the first computer and didn’t even hear about the Z1 to Z4.

But reading up on the details I find that utterly unfair. ENIAC e as way too far away from a programmable machine. It was computation units which just got wired together in different fashion. That is very removed from what a computer is today. The Z1 and later is far closer to what we think of as a computer IMHO, with actual programs being fed into it decoded using registers and and ALU etc.