Try 64K on a PDP-11. Or writing assembly to fit into (say) 16K of ROM on a Z-80 or 6502; that's terrifying, because ROM is forever and you do a 6-8 week spin if you make a mistake. (EEPROMs? Sure, at about 8X the cost of a ROM).

Mostly you'd be up against:

- No Intenet to look up reference material. For that you have books. I'm not sure how much of a revolution the online Unix man pages were, but I'd not worked on any other system that had that kind of documentation. Hope you have lots of bookshelf space (I did :-) ).

- No GUIs anywhere. There was Emacs, kind of. Mostly you got along with ed and regexprs.

- Frustrating toolchains; pre-ANSI C, with 7 characters of significant symbols on earlier systems. I don't remember if any Unix debuggers had symbol information, but they were all command-line driven at the assembly level, with no source information. That's okay, you could pretty much tell where you were by the assembly, because the optimizers were terrible.

- Email? Hoo boy. Might as well just go across the hall to talk to somebody, because unless you were on ARPANET that's about all the farther your email would get.

It'd be frustrating, but kind of fun.

Nice things:

- Tinier software. You've got skillz dealing with hundred thousand line programs. Things were smaller back then, mostly.

- No security worries. I don't know whether to laugh or cry, but DES was pretty controversial (the whole 56-bit key thing) and US citizens couldn't say anything to foreigners about crypto. No network, no crypto, right? (Unix passwords were encrypted with a rotor engine similar, and I think that salts came later).

- Boot times are about the same then as now. :-)

128k?!

Heh. Heh heh.

As if.

Try less than 16k. Less than 8k in may cases. Certainly well less than 64k.

Oh, and it was an absolute blast fitting code into that space.

In fact, my first computer of my very own was a 1802 based single board I wire-wrapped my self. I had loads of fun coding up programs in the 1K of RAM I had at first.

Well, it's better than going back in time only to be unemployed.

And besides, there are people who enjoy it: the entire 64k and 4k demoscene categories live because it's an interesting challenge.

You can still find jobs today where you need to fit all code into 512 instructions and you only have 32 or 64 bytes of RAM (e.g. a low-end PIC12 IIRC).