This is not C.

[EliteTK]

A small problem with the description there. Arduino sketches are C++ and NOT C.

Not that it really matters, just thought I would point it out.

Edit: It seems like the language is actually based on a language called "Processing".

[JessieAMorris]

To be fair, it's a custom language based on C/C++.

[EliteTK]

Whatever it is, it certainly is not C and seems far closer to C++. (Apparently it's a language called "Processing"?)

Additionally, C is very dissimilar to C++, so much so that perfectly standards conformant C will often not compile under a C++ compiler, so I feel like grouping the languages together as "C/C++" is misleading to anyone learning C or C++.

[DanNixon]

The Arduino language is C++, specifically what is now known as "Arduino" is C++ with Wiring-like libraries (this provides stuff like digitalWrite, etc). This does not change the fact that it is C++.

Also the Processing language is Java, Java and C++ are very different languages. (Processing is an IDE which the Arduino IDE is based on, but with very different toolchains underneath)

[Potato-Matic]

https://hackaday.com/2015/07/28/embed-with-elliot-there-is-no-arduino-language/

Thought I'd link this here, since it goes into great depth on how the libraries provided by Arduino and a couple of standard AVR libraries are combined with a regular C++ compiler and some pre-processing trickery to make what Arduino refer to as "The Arduino language."

They get into it a bit in the article, but it's entirely possible to preform the same steps with standard tools outside the Arduino IDE to get the same result and I think HaD wrote a tutorial/article specifically on this at some point. I've been meaning to set this up with a makefile myself, and there are other IDEs out there (like platformio) that re-implement the arduino IDE's toolchain. I migrated to platformio myself a while back after I started running into issues with how the trickery Arduino's preprocessor does to make things simpler started to conflict with standard preprocessor features I was trying to use.

EDIT: I think there's a good user-experience lesson to be learned here: There's no limit to the complexity of things you can teach to a beginner, so long as you wrap it up and give it a less scary name. :D

[Potato-Matic]

For anybody interested jumping in under the hood, I dug up the makefile article too:
https://hackaday.com/2015/10/01/arduino-development-theres-a-makefile-for-that/