0 VAR, textpage
0x0f VAR, textpen

80 const pagew
25 const pageh

0xb800 CONST TEXTMEM
: PREP-TEXTCOPY
  MOV ES t& TEXTMEM @+
  MOV AH textpen @+
  MOV DI textpage @+ ;

:ASM fill-page ( char -- )
  POP AX
  PREP-TEXTCOPY
  MOV CX pagew pageh * #
  REPZ STOSW
  NEXT

0 VAR, textpos
: textx textpos @ pagew % ;
: texty textpos @ pagew / ;
: textx! texty pagew * + textpos ! ;
: texty! pagew * textx + textpos ! ;
: nextline texty 1+ pagew * textpos ! ;

: PREP-TEXTCOPY-XY
  PREP-TEXTCOPY
  ADD SI textpos @+ ;

:ASM draw-text ( s -- )
  MOV BX SI
  POP SI
  PREP-TEXTCOPY-XY
L: draw-next-char
  LODSB
  OR AL AL
  JZ 0 @>
  STOSW
  JMP draw-next-char
0 <:
  SUB DI textpage @+
  INC DI
  MOV textpos @+ DI
  MOV SI BX
  NEXT