To write an interfacing program with parallel port or serial port, we need to know the base address of the corresponding port in advance. Normally the base address of LPT1 will be 0x378 and that of LPT2 will be 0x3F8. And most of the home PCs will have only one parallel port with base address 0x378. To write an interfacing program with parallel port or serial port, we need to know the base address of the corresponding port in advance. Normally the base address of LPT1 will be 0x378 and that of LPT2 will be 0x3F8. And most of the home PCs will have only one parallel port with base address 0x378. If only one port is present on the system we can probably assume that the base address is 0x378. And this can be confirmed by checking the Parallel Port properties in Device Manager. To do this, right click on My Computer, select Manage. Select Device Manager from the Computer Management console. Choose Parallel Port from the device tree, right click on it and select "Properties...