C++ Function Assignment grade calculator - c++

Question

my programming lecturer is teaching us how to write functions, terribly I might add, We are to make a program that calculates the grade of a students work. Here are the specs on it.
score 1 is weighted by 0.3,
score 2 is weighted by 0.5, and
score 3 is weighted by 0.2.
If the sum of the scores is greater than or equal to 85 then the Grade is an 'A'.
If the sum of the scores is greater than or equal to 75 then the Grade is a 'B'.
If the sum of the scores is greater than or equal to 65 then the Grade is a 'C'.
If the sum of the scores is greater than or equal to 50 then the Grade is a 'P'.
Otherwise the Grade is an 'F'.
So I wrote my code as follows:
#include <iostream>
using namespace std;
void calculateGrade() {
int score1, score2, score3;
int percentDec;
cin >>score1>>score2>>score3;
percentDec = (score1+score2+score3);
if (percentDec >= 85) {
cout << "The Course grade is: A";
}
else if (percentDec >= 75) {
cout << "The Course grade is: B";
}
else if (percentDec >= 65) {
cout <<"The Course grade is: C";
}
else if (percentDec >= 50) {
cout <<"The Course grade is: P";
}
else {
cout <<"The Course grade is: F";
}
} //end of calculateGrade()
int main() {
calculateGrade();
return 0;
}
Which works fine on my IDE but when I put it into the program which determines whether our answer is correct it doesn't work, that is because ordinarily we are asked only to put the stuff in main() but because it is a function and it's not in the main() it doesn't work like that. We are given this as an example and I'm about to throw something with how dumb this is. I don't know how to program it to work the way they want it.
cout << "The Course grade is: " << calculateGrade(90, 50, 99) << endl;
Cheers for any help.

Answer 1

This is not a forum for getting answers to your homework questions, although good job on showing what you have tried. Here are areas to look at:
1) The instructor is showing you that you can decompose code into functions. He/she wants you to wrtie a function calculateGrade that would work like this cout << "The Course grade is: " << calculateGrade(90, 50, 99) << endl;. Now every function declaration in C++ has three parts to it:
return_type functionName(param1_type param1, param2_type param2,...) {
// implementation
}
The functionName is what the function is referred to by (calculateGrade in this case), the parameters are the information you need to pass to the function for it to do its thing, and the return type is what the function will give back. In this case, your instructor is saying calculateGrade will take three integers as parameters and must return a string representing the grade of the student's scores. Thus your function should look like:
string calculateGrade(int score1, int score2, int score3) {
// ...
}
2) As the comments rightly pointed out, you aren't multiplying score1, score2, and score3 by their respective weights in the calculateGrade() method.
From your question and comments, I get the feeling your grasp of functions is not completely solid. Rather than complaining about your teacher (be it his/her fault or not), I suggest you read here about it. There are a plethora of online resources that will help you learn the basics of C++ programming.

Answer 2

You tutor is asking you to write a function which accept 3 parameter and return the grade.
char calculateGrade(int score1, int score2, int score3) {
char grade = 'F';
double percent = (0.3*score1 + 0.5*score2 + 0.2*score3);
if(...) {
grade = 'A/B/C/P'; // Depending upon condition, assign only value
}
else if(...) {
grade = 'A/B/C/P'; //Depending upon condition, assign only one value
}
// Add the condition in if else statements to get the actual grade.
return grade;
}
Note that the percent is of type double. You need to do all comparison in if else on double basis.