A look at pointers.

You cannot be a C programmer without using pointers. It’s the one feature of the language that makes possible much of what you can do in C. Pointers seem to scare novice programmers and it’s true that you can crash a program if you make a mistake, but otherwise they’re not that bad. Pointers as parameters in functions let you change the value of an external variable.

A pointer is just a variable that holds the address of another variable. So here’s my take on pointers.

You define a pointer as a pointer to a variable type like a pointer to an int or a char. There is also a “wildcard” where you define a pointer to a void. That has its uses when passing general pointers into functions. With types, the C compiler can verify assignments.

[perl]int * pInt; // pInt is a pointer to an int
char * pChar; // pChar is a pointer to a char
int a;

void ZeroInt(int * pInt) {
if (pInt) // Check pointer does not have a null value
*pInt = 0;

ZeroInt(&a); // Sets a to 0.[/perl]

That ZeroInt() function is a long-winded way of setting whatever int variable it is called with to zero. Yes you can just do a = 0; but that misses the point. What if a was a struct and the ZeroInt was a function to initialise all the fields of the struct?

Leave a Reply

Your email address will not be published. Required fields are marked *