I was just under the naive impression that the DDRB ("B" port or any other register port) was limited to declaring IO direction.
You set two registers at 255=11111111 Passing PORTB=0 turns them all off =00000000
DDRB is the data direction register for port B. It determines whether each pin is an input or an output.
PORTB is the data register for port B. For output pins, this determines whether the pin is set high or low.
Each of the eight bits of the register corresponds to one of the eight pins of the port. The 0'th (right-most) bit of the register corresponds to PB0. The 7'th (left-most) bit to PB7. If a bit of the DDRB register is set to 1, the corresponding pin is set as an output. If the bit is 0, the pin is an input. The pins default to being inputs (i.e. the bits of DDRB default to 0). If a bit of the PORTB register is set to 1, and the pin is set as an output, the microcontroller will hold the pin high - that is, set it to 5V (or whatever voltage is used to power the microcontroller). If a bit of PORTB is 0, and the pin is an output, the microcontroller will hold the pin low (0V).