BIOSerin v9.4.2 (EEPROM w/ Fancy Graphics)

local component_invoke = component.invoke
local component = component
local computer = computer
local unicode = unicode
function boot_invoke(address, method, ...)
  local result = table.pack(pcall(component_invoke, address, method, ...))
  if not result[1] then
    return nil, result[2]
  else
    return table.unpack(result, 2, result.n)
  end
end

-- backwards compatibility, may remove later
local eeprom = component.list("eeprom")()
computer.getBootAddress = function()
  return boot_invoke(eeprom, "getData")
end
computer.setBootAddress = function(address)
  return boot_invoke(eeprom, "setData", address)
end

do
  local gpu = component.list("gpu", true)()
  local w, h
  if gpu and screen then
    component.invoke(gpu, "bind", screen)
    w, h = component.invoke(gpu, "getResolution")
    component.invoke(gpu, "setResolution", w, h)
    component.invoke(gpu, "setBackground", 0x000000)
    component.invoke(gpu, "setForeground", 0xCC0C0C)
    component.invoke(gpu, "fill", 1, 1, w, h, " ")
  end
  local y = 1
  local function status(msg)
    if gpu and screen then
      component.invoke(gpu, "set", 1, y, msg)
      if y == h then
        component.invoke(gpu, "copy", 1, 2, w, h - 1, 0, -1)
        component.invoke(gpu, "fill", 1, h, w, 1, " ")
      else
        y = y + 1
      end
    end
  end
  component.invoke(gpu, "set", 1, 1, "███ █ █ ███  ██ ███ ███ █ ██ ")
  component.invoke(gpu, "set", 1, 2, "██  ██  █ █  █  ██  ██  █ █ █")
  component.invoke(gpu, "set", 1, 3, "███ █ █ ███ ██  ███ █ █ █ █ █")
  computer.beep(20, 3.5)
  component.invoke(gpu, "set", 1, 5, "Booting in 3,")
  computer.beep(20, 1)
  component.invoke(gpu, "set", 1, 5, "Booting in 2,")
  computer.beep(20, 1)
  component.invoke(gpu, "set", 1, 5, "Booting in 1,")
  computer.beep(20, 1)
  component.invoke(gpu, "set", 1, 5, "Booting in 0,")
end

local function tryLoadFrom(address)
  local handle, reason = boot_invoke(address, "open", "/init.lua")
  if not handle then
    return nil, reason
  end
  local buffer = ""
  repeat
    local data, reason = boot_invoke(address, "read", handle, math.huge)
    if not data and reason then
      return nil, reason
    end
    buffer = buffer .. (data or "")
  until not data
  boot_invoke(address, "close", handle)
  return load(buffer, "=init")
end
local init, reason
if computer.getBootAddress() then
  init, reason = tryLoadFrom(computer.getBootAddress())
end
if not init then
  computer.setBootAddress()
  for address in component.list("filesystem") do
    init, reason = tryLoadFrom(address)
    if init then
      computer.setBootAddress(address)
      break
    end
  end
end
if not init then
  error("FATAL: No bootable medium found." .. (reason and (": " .. tostring(reason)) or ""), 0)
end
computer.beep(1000, 0.2)
init()