PORTb Int_ext0 & OUTPUT_B(x) doubt?

[sf]

Hi, I have the next:

On PortB B0 is used for an external interrupt(Pull-up installed).
B1 to B7 to a 7 segments display.

I have made the next "declarations":
#use fast_io(b)

and in main:
set_tris_b( 0b00000001 );
........

After this, B0 is always input or can change at compile time????
I make this question because this: (tested)
When I output a value to the display on B0 (without making an interrupt intentionally) is 0V, when i do not display any value to the display the 5V back to B0.

For output the value is used: output_B(digit_p[n]);
So, when we set this on code( #use fast_io() and set_tris_x() ) the direction can change without "notification", or change??????

Thank´s on advance.

Note:
pic18f1320
display values : xxxxxxx0
ccs version 4.084

[PCM programmer]

Make a test program. Look at the .LST file.