Quick note: if you want a full-hardware "computer" (screen, keys, cup and I/O stuff) consider buying an old Texas Instruments calculator: models up to Ti86 have a Zilog Z80-similar (ISA-compatible) inside, the TI89 and later have a Motorola 68000 cpu inside.
The Ti86/Ti89 are programmable in both Assembly and BASIC (interpreter on-rom). If you are willing to buy the data cable and fiddle with SDCC (Small-devices C compiler, a "mod" of gcc) you might program them in C as well.
The Ti86/Ti89 are programmable in both Assembly and BASIC (interpreter on-rom). If you are willing to buy the data cable and fiddle with SDCC (Small-devices C compiler, a "mod" of gcc) you might program them in C as well.
Links:
* Ti86: https://en.wikipedia.org/wiki/TI-86
* Ti89: https://en.wikipedia.org/wiki/TI-89_series
* SDCC: http://sdcc.sourceforge.net/