I connected to a linux server with PuTTY and start a screen session, and start matlab with:

```
matlab -nodesktop
```

Then, I run my matlab code as usual. The code will run for hours. So to test whether screen works, I start another PuTTY session and run top. Then, I close PuTTY session with **still-running** Matlab (top shows Matlab at 100% CPU usage) in screen. To my surprise, my Matlab process vanished after I close the aforementioned session. I've tried this a few times, and it seems the same thing happened.

```
screen -ls
```

shows that my screens are there but detached. top also shows that my matlab is not there.

What might be the possible cause of this? Doesn't screen normally should keep on running even I terminate my PuTTY session?