The performance of NULL in the memory of 32-bit operating system is 0x0000 0000 0000 0000 0000 0000 0000 that is, all 32 bits are 0, and its value is actually 0.

So, there is

int I = 0； //Let me be empty

Char c =' \ 0//'\0' also appears as a string of 0 in memory, which is equivalent to 0 and NULL.