[longwave]

As the Z3 cannot perform conditional branches I assume it was difficult or impossible for the hardware at the time to do anything other than move the tape in a linear sequence in a single clock cycle. A stored-program computer that uses a program counter to point to the current instruction (the position on the "tape") seems to be a significant step forward.

[gnufx]

Right. If I recall correctly a proof it was potentially Turing complete is relatively recent and obscure, so it's difficult to consider it a general purpose computer like the SSEM. Credit to Zuse, like the pre-war Polish cryptographers, anyhow.

[blattimwind]

This seems to me like a far more salient distinction than how the program is stored.

Instruction pointer and explicit branching.

The Z3 is still (in a theoretical sense) Turing-complete, even without branching instructions (exponential path construction).

[Squonk42]

Extract from http://www.inf.fu-berlin.de/inst/ag-ki/rojas_home/documents/...

"We can therefore say that, from an abstract theoretical perspective, the computing model of the Z3 is equivalent to the computing model of today's computers. From a practical perspective, and in the way the Z3 was really programmed, it was not equivalent to modern computers."