Dereferencing a null pointer

Question

Why I can\'t dereference a null pointer? That is, why I can\'t read/write memory which address is simply 0?

Does the base pointer of my process have a different addr

Answer 1

C 2011 online draft

6.3.2.3 Pointers
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3 An integer constant expression with the value 0, or such an expression cast to type void *, is called a null pointer constant. ⁶⁶⁾ If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function.

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^{66) The macro NULL is defined in (and other headers) as a null pointer constant; see 7.19.}

Emphasis mine. NULL is defined to be an invalid pointer value that represents a well-defined "nowhere". You can't dereference it because there's nothing to dereference. Note that although the null pointer constant is always 0-valued, the null pointer value doesn't have to be; it can be 0x00000000 or 0xDEADBEEF or something completely different; that's up to the platform.

TL;DR, NULL doesn't represent address 0; it represents "no address".