how i can forcing user to inpute alphabet whith out numbers in c language?

Answer 1

write it in a comment at the top of your code and give a message if the input was invalid...

Answer 2

You can check your input for numbers and repeat getting input if the string contained a number.
The Sololearn playground is different though because the code is run on a server not on your device. For Sololearn Anton Böhler's solution is better :)