> For the complete documentation index, see [llms.txt](https://cpb.gitbook.io/book/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cpb.gitbook.io/book/languages/erlang/misc.md).

# Some interesting facts

* WhatsApp messaging system is build on Erlang, it supports over 800 million users and 30 billion messages per day
* bet365 uses Erlang in their Online Gambling & Betting industry.
* Erlang transports 40% of all telecom data
* Erlang can be used in everywhere on the backend
* 3 of the leading banks are built on Erlang
* 2 of the leading blockchains are built on Erlang

## Example of **Hello World** code written in Erlang compared to other languages

### **Erlang**

```erlang
-module(hello).
-export([hello_world/0]).
hello_world() -> io:fwrite("hello, world\n").
```

After this is done, you'll need more work. Save it as hello.erl and compile it from the erlang shell. Don't forget the full-stop ("period" in American English) at the end of each command, as shown:

```
    Erlang (BEAM) emulator version 4.9.1 [source]
    Eshell V4.9.1  (abort with ^G)
    c(hello).
    {ok,hello}
```

(on Unix systems you start the erlang shell by typing "erl" at the command line. On Windows, open a command prompt window and type "werl", or find the Erlang icon in the programs menu). To run the program from the Erlang shell:

```
    hello:hello_world().
    hello, world
    ok
```

### **JavaScript**

```javascript
"use strict"  // This declares strict mode and using it is a good security practice.
console.log("Hello world!");  // semicolon is not mandatory but recommended
```

### **Kotlin**

```kotlin
fun main(args: Array<String>) {
    println("Hello world!")
}
```

### **Python**

```python
print "Hello world!"
```

### **Ruby**

```ruby
puts "Hello world!"
```