func OctIn(Dev);                \Input from device value of sequence of octets
int  Dev, N, Oct;
[N:= 0;
repeat  Oct:= HexIn(Dev);
        N:= N<<7 + (Oct&$7F);
until   (Oct&$80) = 0;
return N;
];

proc OctOut(Dev, Num, Lev);     \Output value to device as sequence of octets
int  Dev, Num, Lev, Rem;
[Rem:= Num & $7F;
Num:= Num >> 7;
if Num # 0 then OctOut(Dev, Num, Lev+1);
if Lev > 0 then Rem:= Rem + $80;
SetHexDigits(2);
HexOut(Dev, Rem);
ChOut(Dev, ^ );
];

\Device 8 is a circular buffer that can be written and read back.
int N;
[for N:= 0 to $40_0000 do
    [OctOut(8, N, 0);
    if N # OctIn(8) then
        [Text(0, "Error!");  exit];
    ];
OctOut(0, $1F_FFFF, 0);  CrLf(0);
OctOut(0, $20_0000, 0);  CrLf(0);
OctOut(0, $7F, 0);  CrLf(0);
OctOut(0, $4000, 0);  CrLf(0);
OctOut(0, 0, 0);  CrLf(0);
OctOut(0, $3F_FFFE, 0);  CrLf(0);
OctOut(0, $FFFF_FFFF, 0);  CrLf(0);
]