Without any application or root you can simply transform your Android smartphone or tablet into a real Laptop ! Be careful, this method is very, very expensive, you risk paying around 5€ !! And yes! A simple cable USB OTG combined with a USB HUB allows you to do a little setup on Android!
What is a USB OTG cable? It is a cable, usually rather short, which on one side has a port Micro-USB or USB Type-C in order to match all smartphones and its opposite a socket USB female classic. By connecting this cable to your smartphone you can exchange data with various devices.
What is a USB HUB? A USB HUB is simply a multiplier USB ports, it consists of a cable USB male and a box with several ports USB female. Thanks to this accessory you will be able to connect more devices to your smartphone or tablet.
That's all well and good, but what can we connect using these two accessories? Well, roughly everything that plugs into a PC, namely: Keyboard, Mouse, Helmet, all even wirelessly. Or even USB sticks, External hard drives, Card readers, USB Gadgets, and even your Microphone PC such as a Blue Yeti to record high quality sound on your smartphone!
For a hard drive or USB key to be recognized, make sure to format it correctly. FAT 32, if it is not, Android will offer to do it itself, but all data present on it will be deleted.
To force landscape screen orientation on any app including the home screen take a look at this video, it's nicer to be in landscape mode all the time rather than having to constantly rotate your device!
If you are interested in purchasing a USB OTG cable as well as a USB HUB there are several links available in the required items section further down this page.