pb系统中对打印页面的控制（自动翻页，定义打印纸的参数，页面大小等）没有现成的控件，此PBL库是一个通用的打印程序-pb on the printed page, the system control (auto flip, define the parameters of the print paper, page size, etc.) are not readily control, the PBL library is a common printing program