Options to power the Arduino Nano include USB, VIN, and 5 volt pin, meaning you have power options for almost any situation.

The Arduino Nano uses a bootloader for handling programming the MCU, which requires the USB to serial bridge to be disconnected from anything that could interfere with the programming.

This is the SB116, an 8-bit programmer’s calculator powered by an Arduino Nano. It features a 128 x 64 pixel monochrome OLED display and can be powered by either a USB port or three AAA batteries.