Compile Error with Code

I am getting some strange compiler errors with my code and can't seem to figure them I will paste both the code and the class definitions below. I am tried goggling it but to no avail, the only thing I found is my constructor for Grade is wrong somewhere. Any help would be greatly appreciated.

These are the build errors:

Evalution.cpp: In constructor ‘Evaluation::Evaluation(char*, Grade*)’:
Evalution.cpp:20:55: error: no match for call to ‘(Grade) (char [30],    double*)’
     Grades[num](Graded[num].comments,&Graded[num].mark);
                                                       ^
Evalution.cpp: In function ‘std::ostream& operator<<(std::ostream&, const Evaluation&)’:
Evalution.cpp:60:23: error: no matching function for call to ‘Evaluation::display(std::ostream*) const’
  os<<input.display(&os);
                       ^
Evalution.cpp:60:23: note: candidate is:
Evalution.cpp:42:6: note: void Evaluation::display(std::ostream&) const
 void Evaluation::display(std::ostream& os) const{
      ^
Evalution.cpp:42:6: note:   no known conversion for argument 1 from ‘std::ostream* {aka std::basic_ostream<char>*}’ to ‘std::ostream& {aka std::basic_ostream<char>&}’

I will paste both Class Definitions below:

This is the Class Evaluation's definiton:

    #include <iostream>
    #include <cstring>
    #include "Evalution.h"
    Evaluation::Evaluation(){
        code[0]='\0';
        for(int num=0;num<50;num++)
            Grades[num];
    }   
    Evaluation::Evaluation(char coursecode[],Grade Graded[]){
            if(coursecode[0]='\0'&& strlen(coursecode) !=6) {
                for(int num=0;num<50;num++){
                    if(Graded[num].mark < 0)
                Evaluation();
                numgrades=num;
            }
        }
            else{
                strcpy(code,coursecode);
                for(int num=0;num < 50; num++) {
                    Grades[num](Graded[num].comments,&Graded[num].mark);
                    numgrades=num;

            }
        }
    }
    bool Evaluation::empty()const{
        if(code[0]=='\0'){
            for(int num=0;num<numgrades;num++){
                if(Grades[num].mark < 0)
                    return  true;
            }
        }
        else
            return false;
    }
    float Evaluation::calculateAverage() const{
        float total=0;
        for(int num=0;num<=numgrades;num++)
            total+=Grades[num].mark;
        return total/numgrades;
    }
    void Evaluation::display(std::ostream& os) const{
        if(empty())
            return;
        else{
            float average=calculateAverage();
            os<< code << average <<endl;
            for(int num=0;num<=numgrades;num++)
                Grades[num].display(std::cout);
        }
    }   
    bool operator<(const Evaluation& tested, double pass){
        float average=tested.calculateAverage();
        if (average < pass)
            return true;
        else 
            return false;
    }
    std::ostream& operator<<(std::ostream& os, const Evaluation& input){
        os<<input.display(&os);
    }
This is class Grade's definiton:

    #include <iostream>
    #include "Grade.h"
    #include <cstring>
    using namespace std;
    Grade::Grade(){
        mark = 0;
        comments[0] = '\0';
    }
    Grade::Grade(char commented[], double &marked){
        if (commented == '\0' && marked < 0)
            Grade();
        else{
            strcpy(comments, commented);
            mark = marked;
        }
    }
double Grade::get() const{
    return mark;
}
void Grade::display(std::ostream& os) const{
    os << mark <<"-"<< comments << endl;
}

Also if anyone spots logical issues in the Evaluation class please let me known.