#include using namespace std; //TOME A : LESSON 1 /*Hello everyone, I have recently been browsing in the comment section of some C++ lessons. Specificly the lessons reletaed to pointers caught my eye since I was a begginer too once and I was having the same trouble. I would love if someone explained to my WHY would I ever use pointers. That's why I will make a small series of lessons like this in which I will try to explain as best as I can how usefull pointers are and maybe I learn something from the professionals too! DISCLAIMER: forgive me for my english :) ============================================= ////////////START HERE////////////////////// So what I'm about to say is going to bring confort to you because the truth is that pointers are not nesseary to make any program (unless you are working with pre made functions of libraries' or c++'s ). Just like with loops, instead of doing this: */ void loop_example(){ int Counter = 0; while( Counter < 5 ){ cout << Counter++ << endl; } } //You could do this void not_a_loop(){ int Counter =0; cout << Counter++ << endl; cout << Counter++ << endl; cout << Counter++ << endl; cout << Counter++ << endl; cout << Counter++ << endl; } //Or even worse, this void not_a_loop_neither(){ cout << 0 << endl; cout << 1 << endl; cout << 2 << endl; cout << 3 << endl; cout << 4 << endl; } /* All these will give the same output: 0 1 2 3 4 But we can notice a difference right? The code looks rediculus. This is something called hard-coding. When you code something the worst way possible. But instead of the bad look hard-coding has It might also result to performance penalties make the code hard to edit and most importantly what if you suddenly wanted, instead of counting to 4 count to 100. Would you copy and paste 95 more times those lines? No, that's where use use a loop. ////////BASICS FOR POINTERS Pointers the same way, they make your life easier at certain problems you might have! So a POINTER is an integer. Just like any other one, it contains a memory address written in hexidecimal ( Hexidecimal System is a counting system with a total of 16 digits instead of 10. That would be: 0 1 2 3 4 5 6 8 9 A B C D E and F"). The purpose of the variable type at the start is just so the compiler understands better what's going on + to keep track of the size of the variable that it is pointing at. In order to create a pointer the following syntax must be followed. * ; So let's make one: */ void pointer_basics(){ int * ptr; /* We can see that it is almost the same as if we created a variable. In fact this is a variable of type: (int *). The only difference is the *(asterisk) between the type and the name. The specific pointer is uninitialized which means that it points to the adress 0. That's the begining of any adress. Like an entrance to a really lobg coridor! Saddly this is not a valid adress, we can't use it and compiler will give us a warning even if we try to print it. So let's give it a value and make it usefull */ int var = 42; /* Pointers again are variables which store a memory adress of other variables so I made one for a sample. Now I will make the pointer point to the memory this variable. But in order to do that we first need a way to get it from the variable it self. For that purpose we use the '&' operator before the variable: */ &var; cout << &var < adress of * -> value of They result to oposite actions so when they are next to each other they cancel out: &*ptr is the same as ptr Let's use * operator for the first time */ cout << *ptr << endl; // returns the value of a ptr += 1; /*here I made the pointer point to an adress 4 bytes forward because the pointer it self is a integer type it automaticaly multiplies '1' with 4*/ cout << *ptr << endl; //returns the value of b (MAGIC!) ptr += 1; cout << *ptr << endl; //returns the value of c (MORE MAGIC!!) /* this can be explained since a,b,c are declared one after another so their adresses are next door! This might remind to us arrays. In fact that's exactly what arrays do. Being just a block of memory, there is a pointer which points to the start of it. Everytime an you ask for a spesific element e.x. [4] it returns the memory address which is 4 times the size of each element to the right! Not amazed yet? Using the * operator we can treat the pointer as if it was the variable that it points to. */ *ptr -= 20; *ptr = 42; cin>>*ptr; /*Since the pointer points to the memory of c what we are basicaly changing here is the value of c and not the pointer it self. That means that if I now print c, it is going to give the same value as *ptr */ cout << *ptr << " = " << var << endl; /*Cool thing when you see it for the fiest time but it is quite logical if you think about it*/ } ///////BASICS FOR REFERENCIES////////// /* Now that we have covered what pointers are and how they work its time to check out another type of pointer; the REFERENCE. Referencies are pointers but they work differently. Each type has its postives and negatives which we are going to talk about later on. */ void reference_basics(){ /* Referencies are just like another way to call a specific variable. They don't store anything, they have no space in memory and no memory adress. Kind of like an Idea. In order to create one, the following syntax must be applied: & = ; Similarly to regular pointers, their declaration looks like thr declaration of any other variable but with an & between the variable type and reference name. Not to be confused with the & operator. They are not the same thing. If the & follows a variable type then it is a reference otherwise it is the memory of operator.The same goes with the * in regular pointers. Another Observation we can make is that i imediately asigned the reference to a variable. That's something is a MUST DO for referencies. They must be set something from the moment they are created: */ int var = 10; int & ref = var; /*That's all. We have made our reference! Now we can treat it as if it was a variable*/ cout << ref << endl; //print its value ref /=2 ; //edit its value cin >> ref; //store input to it e.t.c. /*Of course since they are the same thing (ref IS var, var is the definition of ref, ref is the voodoo doll of var and vise versa), If ref changes, var changes too. Just like in regular pointers*/ int * ptr = &ref; /*Getting its memory adress it is also possible but That does NOT mean that it haa one. It shares the same adress as var so it actually returns the adress of var*/ } /* That was all I had to say as for the basics of pointers. Follow me to get updated for the next lesson. It took me a lot of time to make this so show me some love <3, peace. */ int main(){ return 0; }

Pointers For Beginners I