C++ - *p vs &p vs p

Question

I am still struggling to understand the difference between *p, &p, and p. From my understanding, * can be thought of "value pointed by", and & as "adress of". In other words, * holds the value while & holds the adress. If this is true, then what is the distinction between *p and p? Doesn't p hold the value of something, just like *p?

Answer 1

The * operator is used for indirection. Indirection means the value in p is interpreted as a memory address and the value at that address is loaded. p is the value of p while *p is the value stored in the memory location pointed by p. When you want to indirectly access the value of an integer i, you can have an integer pointer point to it (int *p = &i) and use that pointer to modify the value of i indirectly (*p = 10).

Answer 2

Here is a diagram.

  &p=0xcafebabe        p=0xfeedbeef         *p=0xdeadbeef    <-- memory address

+--------------+    +---------------+    +----------------+
| p=0xfeedbeef | -> | *p=0xdeadbeef | -> | **p=0x01234567 |  <-- memory contents
+--------------+    +---------------+    +----------------+

So, &p is the address of p, which is 0xcafebabe. The memory location 0xcafebabe stores the value of p, p, which is 0xfeedbeef. That is also the address of *p.

So repeat after me: The value of p is the address of *p.

And, the value of &p is the address of p.

And, the value of *p is the address of **p.

And so on and so forth. So * and & are like opposites, and *&p == p == &*p, unless you do funny things with operator overloading.