Arduino Uno digital pins and the ATmega328 port pins.

    DDRx  - The Port D Data Direction Register - read/write
    PORTx - The Port D Data Register           - read/write
    PINx  - The Port D Input Pins Register     - read only 

Arduino Port
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0 	PD0
1 	PD1
2 	PD2
3 	PD3
4 	PD4
5 	PD5
6 	PD6
7 	PD7

8 	PB0
9 	PB1
10 	PB2
11 	PB3
12 	PB4
13 	PB5

A0 	PC0
A1 	PC1
A2 	PC2
A3 	PC3
A4 	PC4
A5 	PC5