"If you set P1.0 HIGH, (using SETB p1.0) there is no way that MCU will also set P1.1 as high (which is already LOW, let's assume).
Every port pin will retain its status until you change it."

balderdash.

If the two pins are connected the pin set high will only read high if the other pin is high.


"you mean that I have to set the port pin at the beginning of my code? "

Not necessarily, check the reset values of the SFR on the datasheet.

Two previous posts has referred to my favorite link, DO read.

Erik