Page 172 - DCAP507_SYSTEM_SOFTWARE

System Software

Notes we're setting the initial value for ip3, which is where ip3 will point, so that initial value is a
pointer. (In other words, the * in the declaration int *ip3 = &i; is not the contents-of operator, it's
the indicator that ip3 is a pointer.)
If you have a pointer declaration containing an initialization, and you ever have occasion to
break it up into a simple declaration and a conventional assignment, do it like this:

int *ip3;
ip3 = &i;
Don't write
int *ip3;

*ip3 = &i;
or you'll be trying to mix oil and water again.
Also, when we write
int *ip;

although the asterisk affects ip's type, it goes with the identifier name ip, not with the type int on
the left. To declare two pointers at once, the declaration looks like
int *ip1, *ip2;

Some people write pointer declarations like this:
int* ip;
This works for one pointer, because C essentially ignores whitespace. But if you ever write
int* ip1, ip2; /* PROBABLY WRONG */

it will declare one pointer-to-int ip1 and one plain int ip2, which is probably not what you
meant.
What is all of this good for? If it was just for changing variables like i from 5 to 7, it would not
be good for much. What it's good for, among other things, is when for various reasons we don't
know exactly which variable we want to change, just like the bank didn't know exactly which
club member it wanted to send the statement to.

Pointer Variable

Pointer variable is a variable which holds the address of another variable. This concept allows
the indirect access to the objects. A variable can be declared as pointer variable and can point to
the starting byte address of any data-type variable. Thus, the value associated with the pointer
variables is not the content of the memory locations to which it points, but the memory address
of that location.
Following is the way to declare and refer a pointer type variable:
C:

Base-type * pointer -variable-identifier;
The address of any variable can be got by preceding the variable name by an ampersand (& ).

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