Mostly because at the lowest level of computing (machine code and CPU instructions), pointers are the only method (that I know of) of any kind of indirection.
At the lowest level, there are 2 types of references:
CPU registers
memory addresses (pointers)
Every higher level language feature for memory management (references, objects, safe pointers, garbage collection, etc) is just an abstraction over raw pointers
Pointers themselves are really just abstractions over raw integers, whose sole purpose is to index into RAM
With that in mind, pointers to pointers are a natural consequence of any kind of nested object hierarchy (linked lists, trees, objects with references to other objects, etc)
The only other kind of indirection would be self-modifying machine code (like a Wheeler Jump). But the computing world at large has nixed that idea for a multitude of reasons
Mostly because at the lowest level of computing (machine code and CPU instructions), pointers are the only method (that I know of) of any kind of indirection.
At the lowest level, there are 2 types of references:
Every higher level language feature for memory management (references, objects, safe pointers, garbage collection, etc) is just an abstraction over raw pointers
Pointers themselves are really just abstractions over raw integers, whose sole purpose is to index into RAM
With that in mind, pointers to pointers are a natural consequence of any kind of nested object hierarchy (linked lists, trees, objects with references to other objects, etc)
The only other kind of indirection would be self-modifying machine code (like a Wheeler Jump). But the computing world at large has nixed that idea for a multitude of reasons
That’s not a pointer to another pointer, but a pointer to a data structure that happens to contain another pointer.
The distinction is meaningless in the land of Opcode’s and memory addresses
For example, a struct is just an imaginary “overlay” on top of a contiguous section of memory
Say you have a struct
struct Thing { int a; int b; Thing* child; } Thing foo {}You could easily get a reference to
foo->child->bby doing pointer arithmetic*((*((*foo) + size(int)*2)) +size(int))(I’ve not used C much so I’ve probably got the syntax wrong)