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How does “while(*s++ = *t++)” work?

I had the following question during an interview. Can someone please explain it to me?

void question( char *s, char *t)
{
  while (*s++ = *t++);
}

Answer 1

Copies the string, pointer by t to the memory, pointed by s.

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operator= will return the assigned value. t is supposed to point to a NULL-terminated string and s should point to memory, large enough to store that string.

So, the while loop will stop when \0 is hit, which is the end of the string, pointed by t. During this while loop, all chars (different from \0) in t will be copied into s.

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Expanded a little, it’s the same as:

while( *t != '\0' ) // while the current char is not NULL
{
    *s = *t; // copy it into s
    ++s; // increment s, to point to the next byte
    ++t; // increment t, to point to the next char, that will be copied
}
*s = *t; // copy the last char of t - the '\0'