What is the use of y in this c language program

Question

#include<stdio.h>
int square (int number)
{
int y;
y=number*number;
}
main()
{
int x=5;
int result;
result=square(x);
printf("\n%d squared=%d",x,result);
return 0;
}
In this program we are not using y after main function but in its absence it is showing error how the declaration y=number*number working here

Answer 1

the function need a return value, which is missed and if you try to return y, it will return the value since y is a local variable which will have been erased from the stack after the loop has completed its function, so you can just do

return number*number; and skip the use of y