[pacificmint]

There was also that 4k block of memory at $C000. It was in between the ROM blocks, and by default it was totally unused.

Basic couldn't utilize it, but in assembly it was a great area of extra memory, and you could use it without even switching the ROMs off.

[anyfoo]

Yep! For those reasons, it was more or less the "default" target for assembly programs without special requirements. So much so that even as a child I knew "SYS49152" ($C000 in decimal) by heart.

[ako]

Basic interpreter used $a000 to $c000 if I remember correctly, and screen buffer characters was at $400. If you didn’t need to display anything you could use it for something else.