I was just reading a bit about the HQ9+ programming language:

* <https://esolangs.org/wiki/HQ9+>,
* <https://en.wikipedia.org/wiki/HQ9+>, and
* <https://cliffle.com/esoterica/hq9plus>,

and it tells me something about a so-called “accumulator” which can be incremented, but not accessed. Also, using `+` doesn't manipulate the result, so that the input

```
H+H

```

gives the result:

```
Hello World
Hello World

```

Can anyone explain me how this works, what it does, and whether it makes any sense? Thanks.