do
local tTasks,nPid,nTimeout,cPid = {},1,0.25,0 -- table of tasks, next process ID, event timeout, current PID
function os.spawn(f,n) -- creates a process from function *f* with name *n*
 tTasks[nPid] = {
  c=coroutine.create(f), -- actual coroutine
  n=n, -- process name
  p=nPid, -- process PID
  P=cPid, -- parent PID
  e={} -- environment variables
 }
 if tTasks[cPid] then
  for k,v in pairs(tTasks[cPid].e) do
   tTasks[nPid].e[k] = tTasks[nPid].e[k] or v
  end
 end
 nPid = nPid + 1
 return nPid - 1
end
function os.kill(pid) -- removes process *pid* from the task list
 tTasks[pid] = nil
end
function os.pid() -- returns the current process' PID
 return cPid
end
function os.tasks() -- returns a table of process IDs
 local rt = {}
 for k,v in pairs(tTasks) do
  rt[#rt+1] = k
 end
 return rt
end
function os.taskInfo(pid) -- returns info on process *pid* as a table with name and parent values
 pid = pid or os.pid()
 if not tTasks[pid] then return false end
 return {name=tTasks[pid].n,parent=tTasks[pid].P}
end
function os.sched() -- the actual scheduler function
 os.sched = nil
 while #tTasks > 0 do
  local tEv = {computer.pullSignal(nTimeout)}
  for k,v in pairs(tTasks) do
   if coroutine.status(v.c) ~= "dead" then
    cPid = k
    coroutine.resume(v.c,table.unpack(tEv))
   else
    tTasks[k] = nil
   end
  end
 end
end
function os.setenv(k,v) -- set's the current process' environment variable *k* to *v*, which is passed to children
 if tTasks[cPid] then
  tTasks[cPid].e[k] = v
 end
end
function os.getenv(k) -- gets a process' *k* environment variable
 if tTasks[cPid] then
  return tTasks[cPid].e[k]
 end
end
end