ORG &HC000
LD HL,TEXT
PRINT: LD A,(HL)
INC HL
AND A
JP Z,ENDPRINT
CALL CHPUT
JP PRINT
ENDPRINT:
END

TEKST: DEFB "Dit is WBASS2",13,10,0
CHPUT: EQU &HA2

so basically you can put a character that is stored in A into screen by doing:
call $a2

also check:
http://map.tni.nl/

and this article to readout the keyboard:
http://map.tni.nl/articles/keymatrix.php