Then, when we'll run this code we will declare the function in our main memory (RAM) and a pointer to this function will be stored in the stack.

![Stack vs Heap](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/3qs9xlb5p56vu9dap2w7.png)
Img Ref:- [Link](https://www.alexhyett.com/stack-vs-heap-memory/)

✨ So, stack is a scope level memory space where your variables like a and b (Local variables) will be stored and heap is a dynamic memory where the pointers, dynamic arrays and objects (instances of classes) gets stored.

📌 Stack gets cleared when a function's executions gets completed like it will be flushed but heap requires a manual cleaning in some programming languages and in some we have garbage collection.

![Meme](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/zxu5rpxrvyohaiumtip9.png)

**Don't worry, follow along you'll get for sure, and please like and save the article to support us**

😎 Now, we know stack, heap which is used to store on the go things when your program runs.

But what about our man who carries whole stuff?? Thread right.

So, thread has thread block 

![Thread Block](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/ad0x2p31wk2syl8ij5pj.png)

So, thread block has some fields and a kind of storage unit only which has some info to run a program and access some shared space or its own space. Shared space is heap memory space and its own space is stack.

-------

💀 Now, comes the part what is an Event Loop and Thread pool.

When someone works in Javascript he/she might have known that JavaScript is a single threaded language which simply means is that whatever your code is it will be carried by a single worker.

But if someone is working in Java, C, C++ etc there we have multiple threads that can be used in parallel.

![Meme What is that](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/x326tviqtexwhprk6adu.png)

Have some patience guys, you will understand 💯

## 📌 Multithreading

Now, let's say you have two functions (in JAVA)

```JAVA


class Main{

public void static main(String[] args){
     System.out.println("Hello world");
}

public static void add(int a, int b){
     System.out.println(a+b);
}

public static void substract(int a, int b){
     System.out.println(a-b);
}

}

function add(){
    setTimeout(()->{
         console.log("I am lazy");
    }, 1000);
    console.log("I am active");
}

setTimeout(()->{
         console.log("I am lazy");
    }, 1000);

console.log("I am active");

let filePath = "test.txt";
let fileContent = fs.readFile(filePath, "utf-8", (data, err)->{
    return data;
})

byte[] buff;

(data, err)->{
    return data;
}