What is error of my code?

Question

√
https://code.sololearn.com/cao0k6bxZcr4/?ref=app

Answer 1

you need to include math.h to use sqrt
#include<math.h>

Answer 2

As mentioned, you need to include math.h

#include <math.h>

at the top of your file. However the way you currently implement the square root case won't work, as the √ is outside the range the type char can handle. Another thing: It's bad practice to put the default case somewhere in the middle of your switch, always try to put it at the end unless you have a good reason not to.