hw to interface 8051 to a pc on serial ports?
plz specify in detail i dont know much about it?

 

If you will communicate with a PC you must use a RS232 level translator. A very common chip for this is a MAX232 type chip. Just Google max232. Also have attention to details. Like if the transmission rate you use is compatible with your CPU clock frequency.
Also Google is your friend. If you Google the phrase 8051 rs232 you will find tons of examples

 

Through a MAX232 you connect to PC comport and communication with PC
Through Google you search MAX232 data sheet and read data sheet

than if problem please send thread