How to update multiple outputs simultaneously
Yes, the ports of an Uno are addressed in C/C++ as PORTB, PORTC, and PORTD respectively, each 8 bits wide. You can read them or assign to them. Other processors' ports have similar names. Of course the pins' port assignments and functions differ from one to the other, which is one reason for providing the single-pin pinMode() and digitalRead(), digitalWrite() functions. But where you need to deal directly with the hardware (and probably don't care about chip-to-chip portability), the registers are exposed with the above symbols.

Also note that most other CPU registers are exposed the same way - the ports' data-direction registers as DDRA, DDRB, DDRC. You may not care about setting them up simultaneously, but if you wanted to make all of your hardware accesses similarly (and save the flash space for the portable pin functions), you could.

Update: 


  Is there a specific command I can use ? Such as Write PortD ?


Yes, you can use the PORTx names like any other C/C++ variable:
PORTD = 0xFF;
PORTD ^= 0x02;
if( (PORTD &amp; 0x40) != 0 ){, for just a couple of examples - just like real C! :-) 

PS: Pighixxx makes absolutely top-notch pinout diagrams for boards &amp; processors. Here is his diagram for the 28-pin DIP-packaged AtMega328p for instance. They're extremely useful when you're working with a chip at the port or board level.