Memory Address and Content

Memory is used to store data, address, and code.

• data: variable, array, structure, string, ...
• address: pointer which points to data or functions
• code: function

Variable

If v is a normal variable, &v is the address of v and v is the content of v.

• &v is fixed.
• v is changeable.
• It's obvious that &v and v are different.
• It's confusing that v is the name of a variable and its content.

Data - Array

If a[i] is a variable in an array a[], &a[i] is the address of a[i] and a[i] is the content of a[i].

• a[i] is a variable. &a[i] is its address, and a[i] is its content.
• a is also the address of a[0], so a and &a[0] can be used interchangeably.
• However, it is convenient but confusing if we use a instead of &a[0].
• When coding, there is a trade-off between a and &a[]
• &a[]: logical, easy to understand
• a: simple, compact, and concise, but confusing

Code - Function

If f() is a function, &f is the address of f(), and the content of f() is code.

• It's confusing that both f and &f are the address of f().

Address - Pointer

If p is a pointer variable, &p is the address of p and p is the content of p.

• both a normal variable and a pointer variable are variables.
• the difference between a normal variable v and a pointer variable p is that p needs a target.
• p is the address of the target. *p is the content of the target
• &p is fixed, p is changeable, and *p is changeable.

Pointer to Nothing

Pointer to Variable

Pointer to Array

Pointer to Function

Pointer to Pointer to Variable