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When I took a look at how the arduino libraries were coded I expected to see register names like I/O registers(PINx,DDRx,PORTx) and other such registers with values assigned to them but instead I saw normal C code with functions and a class.

Why isn't there any embedded C in the structure of the library? Am I misunderstanding something very basic? Please help me understand.

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If you take a look at the Arduino core library (e.g., the AVR version of wiring.c), you will see lots of low-level register access. That's why the core code is specific to a processor architecture.

Other libraries are built on top of the core API in order to be portable.

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    Then why do people even code using low-level registers when they can just use the core API? – Roshan Aug 23 '18 at 10:00
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    @Roshan: 1. Performance: digitalWrite(), for example, is more than 100 times slower than direct port access. 2. Hardware features: the core only provides access to the most generic stuff, you can fully exploit the hardware capabilities only if you access the hardware directly. – Edgar Bonet Aug 23 '18 at 10:05
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Because the Arduino API abstracts those things.

If you put that kind of low-level code into a library the library becomes non-portable. By sticking to the Arduino API (digitalWrite, pinMode, etc) the library can be used on all boards.

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