GeeDeexd:
C:\Users\Dennis\Documents\Arduino\sketch_may22b\sketch_may22b.ino: In function 'void setup()':sketch_may22b:4: error: 'Keyboard' not found. Does your sketch include the line '#include <Keyboard.h>'?
Keyboard.println('Written by GeeDees Arduino');^
exit status 1
'Keyboard' not found. Does your sketch include the line '#include <Keyboard.h>'?
The Arduino Uno board is not compatible with the Keyboard library, which is why you got this error.
From Keyboard - Arduino Reference
These core libraries allow the 32u4 and SAMD based boards (Leonardo, Esplora, Zero, Due and MKR Family) to appear as a native Mouse and/or Keyboard to a connected computer.
Another popular board with native USB is the Pro Micro (or Micro).