import "io"

/*
   devctl(DC_TAPE_LOAD, unit#, "filename", 'R' or 'W')
   devctl(DC_TAPE_READ, unit#, buffer)
   devctl(DC_TAPE_WRITE, unit#, buffer, blocksizeinbytes)
   devctl(DC_TAPE_UNLOAD, unit#)

all return codes pos or zero = success
negative is error message index
for read, the result is size of block
*/

let buffer = vec(128);
let pos = 0;
let size = 0;

let ropen(fname) be
{ let r = devctl(DC_TAPE_LOAD, 1, fname, 'R');
  if r < 0 then
  { out("code %d from tape load\n", r);
    finish }
  pos := 0 }

let rclose() be
{ let r = devctl(DC_TAPE_UNLOAD, 1);
  if r < 0 then
  { out("code %d from tape unload\n", r);
    finish } }

let rchar() be
{ let c;
  if pos = size then
  { let r = devctl(DC_TAPE_READ, 1, buffer);
    if r < 0 then
    { out("code %d from tape read\n", r);
      finish }
    pos := 0;
    size := r }
  if pos = size then
    resultis -1;
  c := byte pos of buffer;
  pos +:= 1;
  resultis c }

let rnum() be
{ let n = 0, c = rchar();
  while c < ' ' do
    c := rchar();
  while c >= '0' /\ c <= '9' do
  { n := n * 10 + c - '0'; 
    c := rchar() }
  resultis n }

let start() be
{ ropen("numbers.txt");
  while true do
  { let n = rnum();
    out("The number is %d\n", n) }
  rclose() }