This is dated 1950, when the Manchester "Baby" was working, but the Mark I wasn't working yet. This was five years after Von Neumann's original draft of the EDVAC design. The EDVAC itself was delivered in 1949. Actual EDVAC report [2] (reset in Tex for readability) [3].
The EDVAC report is something everyone in computer science should read, if they haven't already.
The big problem in the early days was memory. Early memory systems were not only small, but were usually delay lines, where you have to wait for the slot you want to come around, like a disk. Not random access. Both the EDVAC and the MARK I had some true CRT-type random access memory, but not much of it. The Mark I had an index register, which was missing from the EDVAC. That was the last essential piece of CPU architecture needed to make programming reasonably sane. Otherwise you had to store into your program code to index.
The EDVAC report is something everyone in computer science should read, if they haven't already.
The big problem in the early days was memory. Early memory systems were not only small, but were usually delay lines, where you have to wait for the slot you want to come around, like a disk. Not random access. Both the EDVAC and the MARK I had some true CRT-type random access memory, but not much of it. The Mark I had an index register, which was missing from the EDVAC. That was the last essential piece of CPU architecture needed to make programming reasonably sane. Otherwise you had to store into your program code to index.
[1] https://en.wikipedia.org/wiki/First_Draft_of_a_Report_on_the...
[2] https://archive.org/details/firstdraftofrepo00vonn
[3] https://archive.org/details/vnedvac