A status word describes what the I/O device is doing. Each statusword bit indicates a particular condition, such as message data are ready for transmission, device is busy, device is unavailable, or transmission errors. However, in contrast, a command word controls the actual operation of the device. Each commandword bit has its own function, such as stopping the motor, incrementing a feed, or changing the transmission rate.; 一種描述輸入輸出設備正在做什么的狀態(tài)字。狀態(tài)字的每一位對應一個具體的條件,例 如信息數據準備好等待傳輸、設備忙、設備不能用或傳輸出錯等。輸入輸出命令字則相 反,它控制設備的實際操作。命令字的每一位都有它自己的功能,例如停止馬達、進一行或 改變傳輸率等。