The Arduino Nano and Uno are equipped with very similar processors (the chip that essentially serves as the brain of the board). The Nano features an ATmega328, while the Uno sports an ATmega328P.

[Damian Peckett] has implemented an Apple ][, its 6502 processor, and a cassette port, all on an Arduino Uno. If that wasn ... 4KB of RAM and 8KB of ROM. The ATmega328 has only 2KB of RAM ...

Each of the 14 digital pins on the Arduino Uno can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive ...

In one of the lowest spec examples of the last one, [gvl610] has got an up-to-date Linux kernel to boot on a vanilla Arduino Uno ... as the ATmega328 in the Uno has no MMU and is in to way ...

Note: Pin D9 on the Arduino is not the same pin 9 on the ATmega328 IC. Pin 15 on the IC is actually the pin for Digital Pin 9 (D9) on the Arduino. If you want to see the pinout for the ATmega328 IC, ...

Apart from understanding the Arduino's code ... similar to the iconic Uno in a lot of ways. For instance, it's based on the same microcontroller, uses almost identical pinout configuration ...