SE250:HTTB:Pointers:Pointer arithmetic

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Arithmetic Operations that can be performed on pointers include:

Incrementing:

Incrementing a pointer increases the value of what the pointer is pointing to by 1. The increment operator is (++).
Eg.

int *x;
int arr[6];
x = &arr[2];
x++;

So x will be pointing to the 3rd element in the array initially, after the increment, it will therefore point to the 4th element in the array.
Note: In the diagram x is the value pointer is pointing at initially and x2 is the value its pointing at post increment.
Ie.
<html> <img src='http://img114.imageshack.us/img114/4522/incptrxd0.png'> </html>

*Just to clarify, incrementing will not increase the value, but the address being pointed to.

Decrementing

Decrementing is the opposite of incrementing, instead of increasing the value of the pointer by 1, it decreases the value by 1. The decrement operator is (--).
Eg.

int *x;
int arr[6];
x = &arr[2];
--x;

So x will be pointing to the 3rd element in the array initially and after decrementing, it will therefore point to the 3rd element in the array. Note: In the diagram x is the value pointer is pointing at initially and x2 is the value it’s pointing at post decrement.
Ie.
<html> <img src='http://img114.imageshack.us/img114/2200/decptrjj5.png'> </html>

Addition

You can add an integer to a pointer but you cannot add a pointer to a pointer.
Example:

int *x;
int *y;
int arr[6];
x = &arr[2];
y=x+2;

Here x is pointing to the 3rd element of the array and y will be pointing to the 5th element of the array.
Ie.
<html> <img src='http://img114.imageshack.us/img114/1898/addptrmd5.png'> </html>

Subtraction

Pretty much the opposite of addition…
Example:

int *x;
int *y;
int arr[6];
x = &arr[2];
y=x-2;

Here x is pointing to the 3rd element of the array and y will be pointing to the 1st element of the array.
Ie.
<html> <img src='http://img114.imageshack.us/img114/6645/subptrnx2.png'> </html>

SE250:HTTB:Pointers:Pointer arithmetic

Pointer Arithmetic

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