: _type ( buf -- )
    C<? NOT IF DROP EXIT THEN
    C< DUP 0xd = IF 2DROP EXIT THEN SWAP DUP _zbuf ( c a )
    BEGIN ( c a ) C!+ C< TUCK 0x0d = UNTIL ( c a ) C! ;
( user-facing lines are 1-based )
: T 1- DUP 64 * EDPOS ! _pln ;
: P IBUF _type IBUF EDPOS @ _cpos 64 MOVE BLK!! ;
: _mvln+ ( ln -- move ln 1 line down )
    DUP 14 > IF DROP EXIT THEN
    _lpos DUP 64 + 64 MOVE ;
: _mvln- ( ln -- move ln 1 line up )
    DUP 14 > IF DROP 15 _lpos _zbuf
    ELSE 1+ _lpos DUP 64 - 64 MOVE THEN ;