;Screen Control Assembly Lanuage Routines for VIC-20

        SUBROUTINE _SCREEN

SMTEXT  EQU $00     ;Default Text Screen
SMWIDE  EQU $FF     ;Wide Text Screen (Undefined)

;Set Screen Mode
SETSCR: CMP SMTEXT  ;If Default Text Screen
        BEQ GETSCR  ;Return Return 0
        LDA #$FF    ;Else Return ERROR
        RTS
                    ;Else Return 0
;Get Screen Mode
GETSCR: LDA #0      ;Return 0 (Default Text Mode)
        RTS

;Clear the Screen
CLRSCR  EQU $E55F   ;Aliased to CLSR Routine

;Move Cursor To Home Position
CRSRHM  EQU $E581   ;Aliased to HOME Routine

;Move Cursor to Specified Coordinates
SETPOS: STA $D3     ;Save Cursor Column
        STY $D6     ;Save Cursor Row
        JMP $E587   ;Set Screen Poiners and Return

;Get Cursor Position
GETPOS: LDY $D6     ;Load Cursor Row
        LDA $D3     ;Load Cursor Column
        RTS

;Get Screen Size
GETSIZ: JSR $FFED   ;Call SCREEN Kernal Routine
        TXA         ;Transfer Width to Accumulator
        RTS