What is this error message and how to fix it

[paulpaulson]

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1. Arduino programming language The Arduino basically uses the industry-standard C++ language, implemented by the GNU g++ compiler. For information on basic things like loops, strings, functions, data types, and so on try consulting one of the many online C++ references. Hint: Google "C++ tutorial". The main sketch is C++, however the IDE does do a certain amount of pre-processing (in particular, generating function prototypes for you) before submitting the code to the main C++ compiler (see …