c语言调用函数，求解答

Question

Answer 1

“函数调用相关知识”是这个意思吗？

#include<iostream>
using namespace std;
char judge(int x){
    char c;
    if(x>=90)c='A';
    else if(x>=60)c='B';
    else c='C';
    return c;
}
int main(){
    int x;
    cin>>x;
    cout<<judge(x);
    return 0;
}