写一个程序写3个成绩，然后计算平均值，以及显示用户输入的字母成绩

Question

I am running into 3 errors in my code. On line 12, it is saying that ": is ignored on left of 'const char' when no variable is declared On line 29, '{': no matching token found. On line 6, return type of 'main' should be 'int' instead of 'void' My code is:

/*Write a program to read 3 grades. Grades are between 0-100. Calculate the average, then print the 
following message. */
#include<iostream>

using namespace std;

void main() {
int grade1{};
int grade2{};
int grade3{};
int average{};
int sum{};
const char;

cout << "Enter 3 grades (as a number between 0-100): " << endl;
cin >> grade1 >> grade2 >> grade3;
if (grade1 >= 90)
{
    cout << 'A' << endl;
}
if (grade1 <= 89)
{
    cout << 'B' << endl;
}
if (grade1 <= 79)
{
    cout << 'C' << endl;
}
if (grade1 <= 69)
{
    cout << 'D' << endl;
}
if (grade2 >= 90)
{
    cout << 'A' << endl;
}
if (grade2 <= 89)
{
    cout << 'B' << endl;
}
if (grade2 <= 79)
{
    cout << 'C' << endl;
}
if (grade2 <= 69)
{
    cout << 'D' << endl;
}
if (grade3 >= 90)
{
    cout << 'A' << endl;
}
if (grade3 <= 89)
{
    cout << 'B' << endl;
}
if (grade3 <= 79)
{
    cout << 'C' << endl;
}
if (grade3 <= 69)
{
    cout << 'D' << endl;
}
else
    cout << 'F' << endl;
sum = (grade1 + grade2 + grade3);
average = (sum / 3);
    cout << "Your average is: " << average << endl;
    }

Anyone know what I can do to fix these errors? Please help me out. Thank you: :)

Answer 1

Replace void main() by int main() (that is just how C++ works). Also, what are you trying to do with const char ? You are not declaring any variable and you are not using this line, so you can just remove it.

There is nothing wrong with line 29, after fixing the other two issues, the code works just fine.

Some further remarks:

• avoid using namespace std
• declare your variables at the first point you are using them. For example, write int sum = grade1 + grade2 + grade3;
• Try to avoid code duplication by writing a function that does the grading.
• Use else if instead of if , otherwise a number that is between 70 and 79 is also smaller than 89 and produces unwanted output.

Answer 2

Regarding line 12, it seems that you are trying to declare a constant variable, but there is no name for the variable.

Regarding the error in line 6, the message explains what you could do to resolve it, change the return type of main to int .

Regarding line 29, I don't think there is an error.