Pointer arithmetic allows limited operations on pointers like incrementing, decrementing, addition and subtraction. When a pointer is incremented or decremented, its value changes by the size of the data type. Pointers store addresses, so adding two addresses is illegal as there is no meaning to the result. Subtracting pointers yields the offset between the two addresses. Operations like addition, subtraction on a pointer changes its value based on the data type size. Certain operations like addition of two addresses are illegal for pointers.

1. Pointer Arithmetic
Prepared By: Mr. S. A. Patil
Assistant Professor,PVPIT Budhgaon

2. Pointer Arithmetic
 A pointer in c is an address, which is a numeric value.
 Therefore, we can perform arithmetic operations on a pointer just as you can on a
numeric value.
 A limited set of arithmetic operations can be performed on pointers. A pointer may
be:
1. Incremented ( ++ )
2. Decremented ( — )
3. An integer may be added to a pointer ( + or += )
4. An integer may be subtracted from a pointer ( – or -= )
 Pointers contain addresses. Adding two addresses makes no sense, because there
is no idea what it would point to.
 Subtracting two addresses lets you compute the offset between these two
addresses.

3. Incrementing a Pointer
 If we increment a pointer by 1, the pointer will start pointing to the immediate next
location.
 This is different from the general arithmetic because the value of the pointer will
get increased by the size of the data type to which the pointer is pointing.
 The Rule to increment the pointer is given below:
new_address= current_address + i * size_of(data type)
 Where i is the number by which the pointer get increased.
 We can traverse an array by using pointer.

4. Incrementing a Pointer
Example:
int a=10;
int *p;
p=&a;
p=p+1;
Here suppose address of a is 2010 which is stored in pointer variable p;
We perform increment operation on pointer variable p. then new value of p becomes.
p=p+1*2=2010+2=2012

5. Decrementing Pointer in C
 Like increment, we can decrement a pointer variable. If we decrement a pointer, it
will start pointing to the previous location. The formula of decrementing the
pointer is given below:
new_address= current_address - i * size_of(data type)
Example:
int a=10;
int *p;
p=&a;
p=p-1;
Here suppose address of a is 2010 which is stored in pointer variable p;
We perform decrement operation on pointer variable p. then new value of p becomes.
p=p-1*2=2010-2=2012

6. Pointer Addition
 We can add a value to the pointer variable. The formula of adding value to
pointer is given below:
new_address= current_address + (number * size_of(data type))
Example:
float a=10;
float *p;
p=&a;
p=p+3;
Here suppose address of a is 2410 which is stored in pointer variable p;
We add value 3 in pointer variable p. then new value of p becomes the address.
p=p+(3*4)=2410+12=2422
 We can not add two pointers in each other

7. Pointer Subtraction
 Like pointer addition, we can subtract a value from the pointer variable.
 Subtracting any number from a pointer will give an address.
 The formula of subtracting value from the pointer variable is given below:
new_address= current_address - (number * size_of(data type))
Example:
float a=10;
float *p;
p=&a;
p=p-2;
Here suppose address of a is 2410 which is stored in pointer variable p;
We subtract value 2 from pointer variable p. then new value of p becomes the address.
p=p-(2*2)=2410-4=2406
 We can subtract two pointers from each other to get offset.

8. Illegal arithmetic with pointers
 Address + Address = illegal
 Address * Address = illegal
 Address % Address = illegal
 Address / Address = illegal
 Address & Address = illegal
 Address ^ Address = illegal
 Address | Address = illegal
 ~Address = illegal