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I've been looking for a while inside Arduino's files to find the core library. However, I haven't found them yet. Where on my hard drive can I obtain the core library files (.cpp and .h) necessary for all Arduino code?

Looking around on Google, I couldn't find a way to find the above files. I did see something about getting an .a file while Arduino is compiling, however, that isn't what I want. I want to browse the code and look at functions such as delay to see how they would react when given the values not expected. (i.e. Will my code stall if I use delay(-200); by not being to exit the loop, or will it create a black hole and disrupt the space-time continuum?)

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I was interested in the question, but what I want is the source code for strcpy and strcat in assembler source code. I downloaded the Master Library but I cannot locate anything remotely similar to strcpy or strcat. OR Maybe I cannot see the wood for the trees? –  bobzic Dec 11 '14 at 8:51
@bobzic I suggest that you ask another question specifying which files you want to find. –  Annonomus Penguin Dec 11 '14 at 12:34

3 Answers 3

up vote 7 down vote accepted

The base Arduino source files are in the Arduino installation, under hardware/*/cores/. Source for additional libraries included are in libraries/. Additional files may be found in the sketchbook under its hardware/*/cores/ and libraries/ directories.

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And don't forget /usr/lib/avr/include/ or whatever that translates to on non-Linux systems. –  jippie Mar 21 '14 at 18:04

The code is also available online for those times you don't have the IDE installed:


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On a Mac, the path to the source code folder is:
Arduino.app/Contents/Resources/Java/Hardware/Arduino/Cores/Arduino. I'd expect it would be the same from /Java/ on down in other OSes.

Path to library sources (Arduino-Mac)

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