Understanding Pointers

Pointers are a central feature of the C Programming language. They server as a uniform way to generate references to elements within different data structures. Pointers are a source of confusion for novice programmers, but the underlying concepts are fairly simple.

1.Every pointer has an associated type.

2.Every pointer has a value.

3.Pointers are created with the & operator.

4.Pointers are dereferenced with the * operator.

5.Arrays and pointers are closely related.

6.Casting from one type of pointer to another changes is type but not its value.

If p is a pointer of type char * having value q, then the expression (int *)p + 7 computes q + 28, while (int *)(p + 7) computes q +7.

7.Pointers can also point to function.

The value of a function pointer is the address of the first instruction in the machine-code representation of the function.

Example:

int (*f)(int *);

Thus we see that f is a pointer, as indicated by"(*f)". It is a pointer to a function that has a single int * as an argument, as indicated by "(*f)(int *)".Finally, we see that it is a pointer to a function that takes an int * as an argument and returns int.

int *f(int *);

would be read as:

(int *)  f(int *);

That is, it would be interpreted as a function prototype, declaring a function f that has an int * as its argument and returns an int *.