How to use test same condition for multiple variables in C++ - c++11

Question

#include <iostream>
int main()
{
using namespace std;
int P, C, M, marks;
cout << "Grading System\n\n";
cout << "Enter Marks in Phy\n";
cin >> P;
cout << "Enter Marks in Chem\n";
cin >> C;
cout << "Enter Marks in Maths\n";
cin >> M;
cout << "Grades\n\nPhysics Chemistry Maths\n";
if (marks < 50)
cout << "Fail";
else if (marks <= 60)
cout << "C";
else if (marks <= 70)
cout << "B";
else if (marks <= 80)
cout << "B+";
else if (marks <= 90)
cout << "A";
else if (marks <= 95)
cout << "A+";
else
cout << "Error";
return 0;
}
Is there any way to run above if statement for multiple values of marks like
marks = P
then test for marks = C, marks = M and give output respectively,

Answer 1

You could make your program more modular by implementing the test marks logic in a separate function and name it something like checkGrade and pass as an argument the values you took as input.
For example:
#include <iostream>
using namespace std; //I moved this command outside the main function so it applies globally
void checkGrade(int);
int main()
{
int P, C, M;
cout << "Grading System\n\n";
cout << "Enter Marks in Phy\n";
cin >> P;
cout << "Enter Marks in Chem\n";
cin >> C;
cout << "Enter Marks in Maths\n";
cin >> M;
cout << "Grades\n\nPhysics Chemistry Maths\n";
checkGrade(P);
checkGrade(C);
checkGrade(M);
return 0;
}
void checkGrade(int marks){
if (marks < 50)
cout << "Fail";
else if (marks <= 60)
cout << "C";
else if (marks <= 70)
cout << "B";
else if (marks <= 80)
cout << "B+";
else if (marks <= 90)
cout << "A";
else if (marks <= 95)
cout << "A+";
else{cout << "Error";}
}
Or you could use an array like MadaZZ suggested to eliminate the need to call checkGrade() separately for every user input.

Answer 2

Make an array of marks and a function to check respective grades.
#include <iostream>
using namespace std;
void checkGrade(int marks) //function to check grade
{
if (marks < 50)
cout << "Fail";
else if (marks <= 60)
cout << "C";
else if (marks <= 70)
cout << "B";
else if (marks <= 80){
cout << "B+";
}
else if (marks <= 90){
cout << "A";
}
else if (marks <= 95){
cout << "A+";
}
else{
cout << "Error";
}
}
int main()
{
cout << "Enter no. of students\n\n";
int students;
cin >> students;// Take input of no. of students
int P[students], C[students], M[students]; //Declare array of marks, with each index depicting each student. Size of the array would be the number of students you entered
for( int i = 0; i < students; i++ )
{
cout << "Grading System\n\n";
cout << "Enter Marks in Phy\n";
cin >> P[i];
cout << "Enter Marks in Chem\n";
cin >> C[i];
cout << "Enter Marks in Maths\n";
cin >> M[i];
cout << "Grades\n\nPhysics Chemistry Maths\n";
int count = 3;
while(count) //To check grades in different subjects, the loop runs 'count' number of times ie. for each subject.
{
if(count == 3){
cout<<"\n Grade in Physics ";
checkGrade(P[i]); //Function called to check grade
}
else if(count == 2){
cout<<"\n Grade in Chemistry ";
checkGrade(C[i]); //Function called to check grade
}
else if(count == 1){
cout<<"\n Grade in Maths ";
checkGrade(M[i]); //Function called to check grade
}
count--;
}
}
return 0;
}
The above program stores data for all the students in respective marks array. The checkGrade function takes marks as input and displays the grade one by one. I would suggest you google to learn the concepts and solve some problems.