Software that simulates a physical keyboard is known as a virtual keyboard.
Hence, if you have a touchscreen, you may mimic a genuine keyboard by just pressing the keys.
If your Raspberry Pi industrial PLC has a desktop operating system but you don't have a physical keyboard, you can click on the keys to mimic a genuine keyboard.
Onboard Keyboard
Use following shell commands to install onboard virtual keyboard :
sudo apt update
sudo apt full-upgrade -y
sudo apt install onboard
Once installation is complete, you can access this keyboard from MENU > Universal Access.
There are multiple options available so that you can configure it as per your requirement.