What are real example of " While Loop"

I do not know whether this question should be asked or not but I am confuse. This is reason reason I am asking here.
I wanted to know how do we use while Loop in c language I wrote program and read about while loop in my book.
I thought I should write my own programs

so, I made some examples for while loop

• Keep light On until user closes it
  
• Enter password until the user enters correct password
• Do not stop the machine until its temperature is 30* c
  
• Fill the water in...

What are real example of " While Loop"