Arrays of Pointers
Arrays of Pointers
Pointers may be arrayed like any other data type. The declaration for an int pointer array of size 10 is
int *x[10];
To assign the address of an integer variable called var to the third element of the pointer array, write
x[2] = &var;
To find the value of var, write
*x[2]
If you want to pass an array of pointers into a function, you can use the same method that you use to pass other arrays—simply call the function with the array name without any indexes. For example, a function that can receive array x looks like this:
void display_array(int *q[])
{
int t;
for(t=0; t<10; t++)
printf(”%d “, *q[t]);
}
Remember, q is not a pointer to integers, but rather a pointer to an array of pointers to integers. Therefore you need to declare the parameter q as an array of integer pointers, as just shown. You cannot declare q simply as an integer pointer because that is not what it is. Pointer arrays are often used to hold pointers to strings. You can create a function that outputs an error message given its code number, as shown here:
void syntax_error(int num)
{
static char *err[] = {
“Cannot Open File\n”,
“Read Error\n”,
“Write Error\n”,
“Media Failure\n”
};
printf(”%s”, err[num]);
}
The array err holds pointers to each string. As you can see, printf() inside syntax_error() is called with a character pointer that points to one of the various error messages indexed by the error number passed to the function. For example, if num is passed a 2, the message Write Error is displayed. As a point of interest, note that the command line argument argv is an array of character pointers.
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