On Windows 10 its fairly easy to make any program always open in full screen mode, i.e. fully maximized to occupy the whole screen. All you need do is change the properties of the shortcut you use to launch the program.
You might be launching a program from a shortcut in the Windows menu or from a shortcut on your desktop. The instructions below apply to a desktop shortcut.
Right click the desktop shortcut and choose Properties from the popup menu:
In the Properties dialog that appears change the Run property to Maximized:
Then click OK to save. The next time you run your program it will start fully maximized, occupying the entire screen.
In Windows 10, if you are running the program from the Windows menu, right click the program in the Windows menu and choose Open File Location to browse to the shortcut. Then right click the shortcut and modify the Run property to Maximized as shown above when editing desktop shortcut properties.