# Pointer Arithmetics

> Source: https://learn-c.net/pointer-arithmetics/
> Part of Learn C, free to read.

You previously learned what is a pointer and how to manipulate pointers. In this tutorial you will be learning the arithmetic operations on pointers.
There are multiple arithmetic operations that can be applied on C pointers: ++, –, -, +

### Incrementing a Pointer with (++)

Just like any variable the ++ operation increases the value of that variable. In our case here the variable is a pointer hence when we increase its value we are increasing the address in the memory that pointer points to. 
Let’s combine this operation with an array in our example:

```c
#include <stdio.h>

int main()
{
    int intarray[5] = {10,20,30,40,50};
    
    int i;
    for(i = 0; i < 5; i++)
        printf("intarray[%d] has value %d - and address @ %x\n", i, intarray[i], &intarray[i]);
    
    
    int *intpointer = &intarray[3]; //point to the 4th element in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the address of the 4th element
    
    intpointer++; //now increase the pointer's address so it points to the 5th elemnt in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the address of the 5th element
    
    return 0;
}
```

### Decreasing a Pointer with (–)

Just like in our previous example we increased the pointer’s pointed-to address by one using the ++ operator, we can decrease the address pointed-to by one using the decrement operator (–).

```c
#include <stdio.h>

int main()
{
    int intarray[5] = {10,20,30,40,50};
    
    int i;
    for(i = 0; i < 5; i++)
        printf("intarray[%d] has value %d - and address @ %x\n", i, intarray[i], &intarray[i]);
    
    
    int *intpointer = &intarray[4]; //point to the 5th element in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the address of the 5th element
    
    intpointer--; //now decrease the point's address so it points to the 4th element in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the address of the 4th element
    
    return 0;
}
```

### Adding Pointers with (+)

We previously increased a pointer’s pointed-to address by one. We can also increase it by an integer value such:

```c
#include <stdio.h>

int main()
{
    int intarray[5] = {10,20,30,40,50};
    
    int i;
    for(i = 0; i < 5; i++)
        printf("intarray[%d] has value: %d - and address @ %x\n", i, intarray[i], &intarray[i]);
    
    
    int *intpointer = &intarray[1]; //point to the 2nd element in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the address of the 2nd element
    
    intpointer += 2; //now shift by two the point's address so it points to the 4th element in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the addres of the 4th element
    
    return 0;
}
```

Note how in the output the address shifted by 8 steps in the memory. You might be wondering why?
The answer is simple: Because our pointer is an int-pointer and the size of an int variable is 4 bytes the memory is shift-able by 4 blocks.
In our code we shifted by 2 (added +2) to the initial address so that makes them 2 x 4 byte = 8.

### Subtracting Pointers with (-)

Similarly we can subtract:

```c
#include <stdio.h>

int main()
{
    int intarray[5] = {10,20,30,40,50};
    
    int i;
    for(i = 0; i < 5; i++)
        printf("intarray[%d] has value: %d - and address @ %x\n", i, intarray[i], &intarray[i]);
    
    
    int *intpointer = &intarray[4]; //point to the 5th element in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the address of the 5th element
    
    intpointer -= 2; //now shift by two the point's address so it points to the 3rd element in the array
    printf("address: %x - has value %d\n", intpointer, *intpointer); //print the address of the 3rd element
    
    return 0;
}
```

again the address is shifted by blocks of 4bytes (in case of int).

### Other Operations

There are more operations such as comparison >,