About Pointer in C

Pointer, as one of the most powerful tools in C. There are two most obvious advantages of pointer is fast and convenient. Variable in program need a area has a relative address in the RAM in which stores values. Pointer variable is a new variable that stores the address. We can regard that pointer is just the address. I just say something about those two advantages below.

First, define a integer variable number. If we want to store 5 in number, we can write

int number;
scanf("%d",&number);

Now, let's see how computer works.

1. Allocating a area while giving a address for number.
2. Transforming number to the address in RAM given before.
3. Storing 5 into the address.

We know that value finally is stored in the address. But there are 3 steps. How can we simplify it for making the computer compute faster? Pointer just do it.

Written:

int number;
int *pnumber;
pnumber=&number;
scanf("%d",pnumber);

In this code, we set a additional pointer variable pnumber and store the address of variable number in it. Now, pnumber holds a address pointing to number. Value is stored into the address directly without a converting.

There, We have seen how pointer variable works. Perhaps you are puzzled that the lines in program used pointer is more than the first one. So I bring another example next.

Define a array with 10 elements and store 10 value in each element.
Written in normal way:

int array[10],i=0;
for(;i<10;i++)
    scanf("%d",&array[i]);

It's easy to know that we store 10 value with 10 times converting.
Written with pointer:

int array[10],i=0;
int *parray=array;
for(;i<10;i++,parray++)
    scanf("%d",parray);

The array name is his address as well. So, make the pointer point to array when defining a pointer variable parray. As we all know, value is stored straightway without converting a integer variable to a address. Obviously, it's faster because there is no converting.