1 sig pixel screen: (addr screen), x: int, y: int, color: int
 2 sig read-key kbd: (addr keyboard) -> _/eax: byte
 3 sig draw-grapheme screen: (addr screen), g: grapheme, x: int, y: int, color: int
 4 sig cursor-position screen: (addr screen) -> _/eax: int, _/ecx: int
 5 sig set-cursor-position screen: (addr screen), x: int, y: int
 6 sig clear-stream f: (addr stream _)
 7 sig rewind-stream f: (addr stream _)
 8 sig write f: (addr stream byte), s: (addr array byte)
 9 sig append-byte f: (addr stream byte), n: int
10 sig read-byte s: (addr stream byte) -> _/eax: byte
11 sig stream-empty? s: (addr stream _) -> _/eax: boolean