Osborne One

The first portable PC.

It weighed about 15 Lbs, and stood like a drunken sewing machine.

It had a sealed plastic case -- no ventilation -- a 5-inch CRT, two single sided floppies, and a Z80 CPU running CP/M 2.2.

But what made it a real challenge for programmers was the I/O: it had CentronicsParallel? (as did everyone else) and IEE488 (as did few others) and a serial port -- but they used memory-mapped components for both of these. In order to do anything at all directly with the comms hardware one had to bank switch the bottom 4kb of RAM, do whatever, and switch back before performing any further systems calls (which vectored from PageZero? of memory).

On top of this, the memory mapped components didn't synchronize perfectly with the Zilog CPU, so you had to do things like "read status twice, and if different, read again for tie-breaker" in order to send and receive bytes.

In spite of this, it enjoyed a period of affluence in the market, due in part to the bundled software (WordStar, SuperCalc?, dBase II, and MS Basic) which was not yet popular with other manufacturers.