"Not an allowed type" in Turbo C++

Question

I'm trying to make a grading system.So what i want to do is take 1/3 of the value of outputgrade and add it with 2/3 of the value of outputgrade2, I tried midterm1=(outputgrade()*1/3)+(outputgrade2*2/3) but I receive an error which is

Not an allowed type

Please somebody help me on what to do.

#include<iostream.h>
#include<conio.h>
#include<iomanip.h>

double AAO,Quizzes,Project,MajorExam,Midterm;


void inputprelim()
    {
        clrscr();
        gotoxy(3,4);cout<<"Input Prelim Grade";
        gotoxy(1,6);cout<<"Attendance/Ass./Oral: ";cin>>AAO;
        gotoxy(1,7);cout<<"Project: ";cin>>Project;
        gotoxy(1,8);cout<<"Quizzes: ";cin>>Quizzes;
        gotoxy(1,9);cout<<"Major Exam: ";cin>>MajorExam;
        gotoxy(1,11);cout<<"Prelim Grade: ";
    }

int getgrade(double a, double b, double c, double d)
    {
        double result;
        result=(a*0.10)+(b*0.20)+(c*0.30)+(d*0.40);
        cout<<setprecision(1)<<result;
        return result;
    }
void outputgrade()
    {
        getgrade(AAO,Project,Quizzes,MajorExam);
        getch();
    }
void inputmidterm()
    {
        gotoxy(33,4);cout<<"Input Midterm Grade";
        gotoxy(29,6);cout<<"Attendance/Ass./Oral: ";cin>>AAO;
        gotoxy(29,7);cout<<"Project: ";cin>>Project;
        gotoxy(29,8);cout<<"Quizzes: ";cin>>Quizzes;
        gotoxy(29,9);cout<<"Major Exam: ";cin>>MajorExam;
        gotoxy(29,11);cout<<"Temporary Midterm Grade: ";
        gotoxy(29,12);cout<<"Final Midterm Grade: ";
    }
void outputgrade2()
    {
        getgrade(AAO,Project,Quizzes,MajorExam);
        getch();
    }


void main()
    {
    inputprelim();
    gotoxy(15,11);outputgrade();
    inputmidterm();
    gotoxy(54,11);outputgrade2();
    gotoxy(55,11);
    Midterm1=(outputgrade()*1/3)+(outputgrade2()*2/3);
    }

Answer 1

Your functions outputgrade() and outputgrade2() are of return type void. In order to use them in midterm1=(outputgrade()*1/3)+(outputgrade2*2/3) you need to change their return type as int/double/float,etc.

If I have understood the logic of your code correctly then edit the two functions as:

double outputgrade()
    {
        return getgrade(AAO,Project,Quizzes,MajorExam);
    }

double outputgrade2()
{
    return getgrade(AAO,Project,Quizzes,MajorExam);
}

What I have done is changed the return type to double and at the same time the two functions are now returning whatever value getgrade returns.