The pointers - English version

Pointers

Hello, here is how I see the pointers.

As you know, each variable has a value and an address, when we define a variable, the OS looks for a free address and then gives it to the program. When we want to display the value of the variable, we just write:
int main ()
{
int test = 21;
printf("test is: %d" test);
}

But it is also possible to display the address of the variable with the following code:
int main()
{
int test = 21;
printf("The test address is: %p" test); / * the use of "&" is used to display the test address and not its value * /
}

You probably will say "but of what use is the test adress? »
For example, to return many values ​​from a function, it is possible to store the variable address in a variable called type "pointer", these variables are defined as follows:
int * pointer = NULL;
A pointer is initialized by either the value "NULL" or by an address.
There are now two ways to change the value of the variable "test":
int main()
{
int test = 0;
int *pointer = &test;

test = 45;
printf("test is %d\n", test);

* Pointer -= 2
printf("test is %d", test);
return 0;
}

The result of this code in the terminal will be:

test is 45
test is 43

Indeed, one can modify a variable by changing the pointer of the variable preceded by "*". Now you know how to change multiple variables with a single function!
You will for example need pointers to save text in files, to allow the user to type his first name, to create an identity card ...
I hope you like this presentation.

Romain Lebbadi-Breteau
0696076393
r.lebbadibreteau@icloud.com