Polling(轮询 Determines state of device(决定设备的状态) command- ready(等待命令) BusY(忙) Error(错误) Busy-wait cycle to wait for l/o from device (忙等待循环等待设备的O操作) Applied Operating System Concepts 123 Silberschatz, Galvin, and Gagne @199912.3 Silberschatz, Galvin, and Gagne ©1999 Applied Operating System Concepts Polling(轮询) • Determines state of device (决定设备的状态) – command-ready(等待命令) – Busy(忙) – Error(错误) • Busy-wait cycle to wait for I/O from device (忙等待循环等待设备的I/O操作)