text lookup table

 ORG $4800

 JMP START

LOOKLO DFB #$00,#$80,#$00,#$80
 DFB #$00,#$80,#$00,#$80
 DFB #$28,#$A8,#$28,#$A8
 DFB #$28,#$A8,#$28,#$A8
 DFB #$50,#$D0,#$50,#$D0

LOOKHI DFB #$04,#$04,#$05,#$05
 DFB #$06,#$06,#$07,#$07
 DFB #$04,#$04,#$05,#$05
 DFB #$06,#$06,#$07,#$07
 DFB #$04,#$04,#$05,#$05

XLOCATION DFB #00           ;HORIZONTAL COORDINATE
YLOCATION DFB #00           ;VERTICAL COORDINATE
CHARACTER DFB #00           ;VALUE OF CHARACTER TO DISPLAY

START     LDY YLOCATION
          LDX XLOCATION

          LDA LOOKLO,Y      ;GET TEXT SCREEN 
          STA STOR+1        ;VERTICAL LINE ADDRESS
          LDA LOOKHI,Y      ;AND MODIFY CODE BELOW
          STA STOR+2

          LDA CHARACTER     ;LOAD A WITH CHARACTER TO DISPLAY
STOR      STA $4000,X       ;STORE IT TO SCREEN WITH HORIZ
          RTS               ;VALUE AS OFFSET