Pins with analog inputs are set to analog input mode by default. To read a digital input you must clear the corresponding ANSEL or ANSELH bit. RB0 is AN12, so you need to clear ANS12 (bit 4 in ANSELH).

Pins set to output mode are not affected by the analog input settings.

Pins with analog inputs are set to analog input mode by default. To read a digital input you must clear the corresponding ANSEL or ANSELH bit. RB0 is AN12, so you need to clear ANS12 (bit 4 in ANSELH).

Pins set to output mode are not affected by the analog input settings. However a read-modify-write operation may fail if it needs to know the pin state and the pin is set to analog input mode.