5v inputs to microcontroller

[Build-A-Burger]

I was looking at the thread posted recently by thannara123: https://www.edaboard.com/threads/332224/

and I had a question about the diagram:

what is the purpose of the diodes? Are they 5v? (I didn't want to hijack the thread).

 

[xenos]

Safety reasons. In case the cirquit with the "buttons" may use higher voltages than 5V.
e.g. if the external cirquit has 24V/0V outputs, the 24V will not damage the 4021, because diode will not allow current to flow to 4021.
If the external cirquit has open collector outputs or uses 5V/0V outputs, then the diodes (1N4148 probably) are not required.