That's late for hand coding assembler (and very late for a KIM 1). Last time I did any hand assembly was 81/82 for a ZX81. Graduated to an Apple //e where I wrote my own assembler using the mini-assembler in the integer basic ROM and Apple Writer I as a text editor. By 1984 I had gotten my hands on the Apple ProDOS assembler so my bodged mini-assembler got put out to pasture.

Mind you I've just got an Atari 65XE from ebay today which I will now have to explain to my wife (I always thought the Atari graphics was neat and wanted to play with the display list stuff but never did so at the time)