The default bootloader of the Arduino UNO is optibootbootloader. It is a small, fast, and efficient bootloader that is used to load the Arduino sketch into the microcontroller. It is stored in the microcontroller’s flash memory and is executed when the microcontroller is powered on. The optibootbootloader is a critical part of the Arduino ecosystem and allows users to easily program their Arduino boards.
Air-boot is a bootloader that is used to load the Arduino sketch into the microcontroller without using a programmer. It is a newer bootloader than optibootbootloader and is not as widely supported. Bare box is a bootloader that is used to load the Arduino sketch into the microcontroller without any bootloader. It is the most basic bootloader and is not as widely supported as optibootbootloader or air-boot. Gag is a bootloader that is used to load the Arduino sketch into the microcontroller in a way that prevents it from being programmed again. It is a security feature that is not widely used.
In conclusion, the default bootloader of the Arduino UNO is optibootbootloader. It is a small, fast, and efficient bootloader that is used to load the Arduino sketch into the microcontroller. It is stored in the microcontroller’s flash memory and is executed when the microcontroller is powered on. The optibootbootloader is a critical part of the Arduino ecosystem and allows users to easily program their Arduino boards.