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@ -56,14 +56,14 @@ Now, suppose we have a mechanism that allows us to **manipulate the variable via
Let's see an easy to understand the advantage. Suppose, we want to pass a large variable to a function. Let's see an easy to understand the advantage. Suppose, we want to pass a large variable to a function.
![enter image description here](https://lh3.googleusercontent.com/K9oyNSIl8fTmUsdf4AC5lIUFVobztgrxhADG6rXs7GS7zhusz-SdY7HrVZfsfeMAwl09Aj8h5JVt) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/3.jpg)
Passing via usual way(by value) will create a copy of the large variable. Passing via usual way(by value) will create a copy of the large variable.
![enter image description here](https://lh3.googleusercontent.com/WHxLPqxcNE7DgD9Uw6U8D9wqXQHc4yJYViY0n7Zx6gYjh8uyxWpBoq30ZsdtrYDdi_hmQe8XWGFw=s1500) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/4.png)
But now we will pass the address of a variable and use the mechanism to avoid a copy of the large variable. But now we will pass the address of a variable and use the mechanism to avoid a copy of the large variable.
![enter image description here](https://lh3.googleusercontent.com/pVTSutVudnGliLXtxRiehzA4yw58_ViQsSL-mmLCWgo1hueCdWZg0--q_NszXLYSj2GrOvWZ3O4j=s1100) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/5.png)
So basically, we are passing values indirectly using just the address of a variable. So basically, we are passing values indirectly using just the address of a variable.
@ -117,7 +117,7 @@ The best practice is to declare pointers in different lines.
As we know, pointer variables store the address of another variable. Therefore, **the value must be an address of a predeclared variable of the same datatype as of pointer variable**. As we know, pointer variables store the address of another variable. Therefore, **the value must be an address of a predeclared variable of the same datatype as of pointer variable**.
![enter image description here](https://lh3.googleusercontent.com/RrQ_aBMT55mVHTDmF6VPcZeMPfKe5tIry4EyRYiwiP_nLSfSwF9ajkupEjrB6SJ2zf41ry_zyAuG) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/6.png)
```cpp ```cpp
#include <iostream> #include <iostream>
@ -326,7 +326,7 @@ What did you observe?
You can see that arrays are also using pointer, which points to the first element of the array. You can see that arrays are also using pointer, which points to the first element of the array.
![enter image description here](https://lh3.googleusercontent.com/DJAY3eUjzVFKOl87L0sSBBJmt1T7DcSOgKVGhw823RAdX594C0fzft3HP78lA9UjWXMwTz3QMiBc) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/7.png)
But a fixed array is not exactly a pointer, let's see: But a fixed array is not exactly a pointer, let's see:
@ -361,7 +361,7 @@ Yes, add `sizeof(data type of array)` bytes to the address of the first element
In C++, we can use basic math operations(addition and subtraction) on pointer as well. But it is different. If you add(or subtract) integer $a$ to pointer containing some address, then it will add(or subtract) `a*sizeof(data type of the pointer)`(ex. `a*(4 byte)` for integer pointer) to its address. In C++, we can use basic math operations(addition and subtraction) on pointer as well. But it is different. If you add(or subtract) integer $a$ to pointer containing some address, then it will add(or subtract) `a*sizeof(data type of the pointer)`(ex. `a*(4 byte)` for integer pointer) to its address.
![enter image description here](https://lh3.googleusercontent.com/W3M3lLq_u1iTl2eaWhhD62e5D5LikeVl5IltdfDVXwHyL27dl0KpclcDFiTr0Z7iKRuhQZfTJyEn) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/8.png)
As array elements are continuous(sequential) in memory, **pointer arithmetic is basically used when we access array elements using [] operator(ex. array[3]).** As array elements are continuous(sequential) in memory, **pointer arithmetic is basically used when we access array elements using [] operator(ex. array[3]).**
@ -478,7 +478,7 @@ Now, let's check how well you have understood things so far.
Pointer to Pointer is a pointer that holds the address of another pointer variable. It can be declared by putting two asterisks (`**`) instead of one. Pointer to Pointer is a pointer that holds the address of another pointer variable. It can be declared by putting two asterisks (`**`) instead of one.
![enter image description here](https://lh3.googleusercontent.com/upJucegdzSIqe0uwQrPJdMYH6o9ymRDOg4t8Dyh-3c8JUp4vR-ULkVTIox1Q6HRg98X5NY88jycf=s1500) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/9.png)
```cpp ```cpp
#include <iostream> #include <iostream>
@ -534,7 +534,7 @@ Observe the below image and try to understand the shown pointer arithmetic.
Note that, `a[x][y]` in pointer arithmetic sense is basically `*(*(a+x)+y)`. Note that, `a[x][y]` in pointer arithmetic sense is basically `*(*(a+x)+y)`.
![enter image description here](https://lh3.googleusercontent.com/34Kre8qChbnZsqlSltbsFMxWtSg6WiaLT2zCZpi8am3eqvv-4SUoiOMyHWwnh_-tW13DMeDlx-Vd=s1500) ![enter image description here](https://github.com/KingsGambitLab/Lecture_Notes/blob/master/articles/Akash%20Articles/md/Images/Pointers/10.png)
Here `sizeof(a[0])` or `sizeof(*a)` is 3 integers, i.e. 12 bytes and therefore in pointer arithmetic, if we add 1 to `a`, then it basically adds 12 bytes. Here `sizeof(a[0])` or `sizeof(*a)` is 3 integers, i.e. 12 bytes and therefore in pointer arithmetic, if we add 1 to `a`, then it basically adds 12 bytes.