C.
The most influential programming language that has ever existed.
It powers supercomputers, embedded systems, and every popular software tool you use today.
Learning C will help you unlock a new power that you will never possess by writing Python and JavaScript:
Memory management.
Variable & Virtual Memory
To get started, create a main function and an integer i with a value of 0.
When your program runs, that variable needs to be stored somewhere.
Where is it?
The RAM.
(technically, not the physical RAM but a virtual RAM)
Let’s zoom in a little bit.
Variable i lives in 0×1000.
Notice there’s a 0x in front?
Memory addresses are written in hexadecimal.
Its decimal version looks like this:
The size of an integer is 4 bytes.
So, if you create another variable j.
Its memory address is 1004, instead of 1001.
Pointers
Now let’s talk about a special type of variable called pointers.
A regular variable stores an integer, a character, etc.
A pointer stores a memory address.
Here's how it works.
First, get the memory address of a variable, like i, with the & operator:
&i; //0x1000Assign that value to a new variable called i_ptr.
int* i_ptr = &i;Notice how there’s an asterisk (*) in front?
We need that to create a pointer instead of an integer.
Let’s see what happens in the RAM.
A new variable i_ptr is created.
The only thing special is that its value is a memory address of another variable.
Now you can read and write the value of that variable (int i) through the pointer.
This is how you read it:
*i_ptr; //0And this is how you overwrite it:
*i_ptr = 4;The value of i should become 4.
Let's test it by printing it out.
int main() {
int i = 0;
int *i_ptr = &i;
*i_ptr = 4;
printf("value of i: %d\n", i);
}To run the code, install a C compiler, like gcc.
Compile the code into machine code.
Then run the executable file.
You will see the value of i becomes 4.
value of i: 4And you have just learnt the fundamentals of pointers & memory management in C.
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