OPTION_REG register

The OPTION_REG register is a readable and writable
register, which contains various control bits to configure
the TMR0 prescaler/WDT postscaler (single assignable
register known as the prescaler), the External INT
Interrupt, TMR0 and the weak pull-ups on PORTB.

bit 7:

RBPU: PORTB Pull-up Enable bit
1=PORTB pull-ups are disabled

0= PORTB pull-ups are enabled for all PORTB inputs

Page 12 in the datasheet