[saljam]

This was part of The Baby, AKA the Manchester Small-Scale Experimental Machine at the University of Manchester in the late 40s. Modern replicas and simulators can be found at the university and Manchester's Museum of Science and Industry. It was built by Williams, Kilburn, and Tootill. Alan Turing wrote some programs for this machine.

One nicest things about this is that your memory is visible. You can just see which bits are on and which bits are off by looking at the screen. No debugger needed!

One of the least nice things was that these tubes had a reputation of being horribly unreliable.

[beachy]

Visible memory - useful indeed. As a newly minted mainframe engineer at IBM I worked with a guy who could read from punched paper tape by eye. It was most impressive watching him pulling it through his hands at a pretty good pace, reading it out as he went.

[tomcam]

I worked with Tim Paterson (creator of MS-DOS) when I worked on the Visual Basic team at Microsoft. When he worked on code generation he just read hex dumps, not disassembly, because it was faster for him.

[ams6110]

It doesn't take that long to learn when you have to do it. When I had to write an assembler as an undergrad project I became pretty much able to read 6809 machine code directly.

[tomcam]

32-bit instruction set was much bigger with many more addressing modes