> For the complete documentation index, see [llms.txt](https://longer-vision-robot.gitbook.io/arduino-full-stack/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://longer-vision-robot.gitbook.io/arduino-full-stack/02_programming_grammar/01_avr_c_grammar.md).

# 2.1 AVR C

One of the GCC mplementations for Atmel AVR microcontrollers is [Savannah NonGNU AVR Libc](http://www.nongnu.org/avr-libc/), which is adopted in this course. The manual can be found at <http://www.nongnu.org/avr-libc/user-manual/index.html>.

Two language references are suggested as:

* [Savannah NonGNU AVR Libc Reference](http://www.nongnu.org/avr-libc/user-manual/modules.html)
* [Language Reference on Arduino Office Website](https://www.arduino.cc/en/Reference/HomePage).

In our course, [Language Reference on Arduino Office Website](https://www.arduino.cc/en/Reference/HomePage) is a must read.