Pointer Arithmetic

The pointer holds address of a value, so there can be arithmetic operations on the pointer variable.

Arithmetic operations possible on pointer in C language :

• Increment.
• ecrement.
• Addition.
• Subtraction.

Increment :

• Incrementing a pointer is used in array because it is contiguous memory location.
• Increment operation depends on the data type of the pointer variable.

The formula of incrementing pointer is given below :

    new_address= current_address + i * size_of(data type)

Example :

Incrementing pointer variable on 64 bit OS

    #include <stdio.h>
    #include <conio.h>
    void main()
    {
    int i = 3;
    int *j;//pointer to int

    j = &i;//stores the address of i variable
    printf("Address of i variable is %u \n", j);

    j = j+1; // incrementing pointer by 1(4 bytes)
    printf("After increment: Address of i variable is %u \n",j);
    }

Output :

Address of i variable is 65524
After increment: Address of i variable is 65528
Explanation :
For 32 bit int variable, it will increment to 2 byte.
For 64 bit int variable, it will increment to 4 byte.

Decrement :

The formula of decrementing pointer is given below :

    new_address= current_address - i * size_of(data type)

Example :

    #include <stdio.h>
    #include <conio.h>
    void main()
    {
    int i = 3;
    int *j;//pointer to int

    j = &i;//stores the address of i variable
    printf("Address of i variable is %u \n",j);

    j = j - 1; //decrementing pointer by 1(4 bytes)
    printf("After decrement: Address of i variable is %u \n",j);
    }

Output :

Address of i variable is 65524
After decrement: Address of i variable is 65520

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 + (value * size_of(data type))

Example :

    #include <stdio.h>
    #include <conio.h>
    void main()
    {
    int i = 3;
    int *j;//pointer to int

    j = &i;//stores the address of i variable
    printf("Address of i variable is %u \n", j);

    j = j+3; // incrementing pointer by 4*3=12 bytes
    printf("After increment: Address of i variable is %u \n",j);
    }

Output :

Address of i variable is 65524
After increment: Address of i variable is 65536

Explanation :

For 32 bit int variable, it will add 2 * number.
For 64 bit int variable, it will add 4 * number.

Pointer Subtraction

Like pointer addition, we can subtract a value from the pointer variable.

The formula of subtracting value from pointer variable is given below :

    new_address= current_address - (value * size_of(data type))

Example :

    #include <stdio.h>
    #include <conio.h>
    void main()
    {
    int i = 3;
    int *j;//pointer to int

    j = &i;//stores the address of i variable
    printf("Address of i variable is %u \n", j);

    j = j - 3; // decrementing pointer by 4*3=12 bytes
    printf("After increment: Address of i variable is %u \n",j);
    }

Output :

Address of i variable is 65524
After increment: Address of i variable is 65512