This page assumes nothing. Before you touch [[Pointers — declaration, dereferencing ( - ), address-of (&)|the parent note]], we build every symbol it uses — the variable, the byte, the address, the two operators & and *, the type tag, and NULL — one on top of the last. If a symbol appears in the parent, it is earned here first.
Look at the figure. The street runs left to right. Every house is one byte. The number under each house is its address — it never changes. The stuff inside a house is its contents — that can change.
The name x is a convenience for you. The machine only knows the address. So a variable is really a (name, address, value) bundle — and the address is the part beginners never see, yet it is the whole game.
WHY the topic needs this: an address alone (say 0x1000) is not enough to read a value — it only says where to start. You also need to know how many bytes to grab and how to interpret them. That is exactly the extra information a pointer's type carries, and it is why int * and char * are different even though both hold "just a number".
WHY a whole operator for this: without &, you could never obtain an address to store or pass along. & is the only door from the world of names into the world of addresses.
Look at the red arrow in the figure: it starts at the name x and points down to its address number. That downward "what's your house number?" motion is precisely &.
Now we have addresses (numbers). Where do we keep one? In a variable — but a special variable that promises "the number I hold is an address, and it points at an int".
WHY we need it: & got us the address; without * an address would be a dead number we could never use. * is the return trip — from a house-number back to the stuff inside that house.
Trace the figure: p holds the number 0x1000 (top box). The red arrow jumps from p to the house at 0x1000 and reads 42. That jump is*p.
WHY the topic needs it: a pointer that was never aimed anywhere holds garbage — a random number that may name a forbidden house. NULL gives you a safe, checkable "empty" value so you can guard if (p != NULL) ... before travelling.
Read it upward from the bottom: the parent topic stands on the inverse identity, on NULL, and on dereferencing — each of which rests on the pointer box, which rests on address + type, which rest on the byte-street. No layer is skipped.
