| 摘要 |
PROBLEM TO BE SOLVED: To securely recognize that the power source of a printer connected to a host computer is OFF by writing a plurality of power-OFF values into a printer monitor program and comparing them with a plurality of interface signal values of a parallel interface. SOLUTION: On a hard disk 21 in the host computer, the print monitor program is installed. A CPU 22 reads centronics information out of a parallel status port 24 of a centronics port 23 from which the information of the centronics (parallel) interface connected to the printer can be read out. The read information is compared with the power-OFF values previously entered into the program and verified. The printer monitor program displays the state wherein the power source of the printer is OFF on the display device of the host computer when the read state information of the printer matches a printer power-OFF value entered into the program.
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