Sqr

Question

What’s that mean || Int(*fp)(int)=sqr ???

Answer 1

int (*fp)(int) x;

declares a pointer to a function of return type int, which takes one argument of type int. What you can achieve with this, is to create aliases to existing functions, such as

int func(int p) { return p+1; }

int (*fp)(int) x = func;

You can then call func() using x.

printf("%d", x(39));
// prints 40

Somewhat identical:
https://code.sololearn.com/c7yvjIx5hWsw/?ref=app