usb print is for printing via usb under xp

通过Windows系统的API函数SetupDi族函数，获得USB针式打印机的句柄，然后在通过CreateFile，WriteFile函数向该打印机发送指令，以达到控制打印的目的。-SetupDi family of functions through Windows API function system, get a handle USB dot matrix printer, and then send commands to the printer through CreateFile,