Dear sir i am new for 8051 microcontroller.......i am fullly confused about port configuration on MCu.....plz explain me that why we write 0xff to make a port as i/p or o/p...what is the basis concept of it.....what is the hardware profile of 8051 mcu..

 

It is fully explained in the data sheet. You should try reading one sometime. A `1' written to the port data latch enables a weak pullup. This weak pullup establishes either an output logic `1' or can be pulled low by a typical external output driver.

Could you elaborate on the precise meaning of "hardware profile". I am not familiar with that term.

 

You need to configure I/o port pins as inputs or outputs.
Sending a 1 to the config address makes it an output and a 0 makes it an input.