In this post on the Arduino.cc forums and this blog post, [Majek] announced that he had fooled the AVR microcontroller inside and Arduino into writing user data into its own flash memory during run… ...

He’s tested this with a 16F628 and is happy to report that he can successfully flash the program memory, ... Douglas, here is an Arduino PIC programmer which has its own 12V boost converter.

Arduino has also upgraded the onboard flash storage pool. The Uno R4 features 256 kilobytes of solid-state memory, eight times more than the previous-generation chip.

The bootloader, however, occupies 2 KB of the flash memory, so you essentially have 30 KB of usable space left for your sketches. The Raspberry Pi Pico is fitted with the Raspberry Pi-made RP2040 ...