Program question---

**d21998** · 05-15-2002

This is the only time I will post a question of this sort. I've done some small programs and I'm learning this on my own. I want to be able to disect a grading program. the one in question follows:

A program that prompts a user to enter a 2 digit Student ID (an integer ie 01) and a grade (a decimal number ie 89.72). After each entry, display the student’s letter grade and prompt user to either continue with input or stop input. Loop until user has no more entries.

Use the following table to calculate and display each student’s letter grade:
A 90-100
B 80-89
C 70-79
D 60-69
F 0-59

I'm not familiar with looping yet. Could someone please help out? If not I understand completely... Thanks..

**DISGUISED** · 05-15-2002

There are several ways to do this. Here is an easy method.

Code:

#include <iostream>
using namespace std; 

int main() 
{ 
   char choice = 'y'; 
   while(tolower(choice) == 'y') 
   { 
      //do stuff
      cout<<"\nContinue?(y/n):"; 
      cin>>choice;
   }
   return 0; 
}

**Mario** · 05-15-2002

Also testing against the table of grades can be easily done with a switch

**tudehopet** · 05-18-2002

I dont think a switch statement would be suggestable.

I would rather go with an if statement.

**Mario** · 05-18-2002

hmm... given that you have 5 possible letter grades wouldn't that mean cascading IFs, making it harder to read?

**tudehopet** · 05-18-2002

Well, I still don't see how a switch statement would work.

Heres what I was thinking:

char grade;
if (mark > 100 || mark < 0)
{
cout << "error" //validation
return 0; //exit
}
else if (mark > 89 && mark < 101)
grade = 'A';
else if (mark > 79 && mark < 90)
grade = 'B';
else if (mark > 69 && mark < 80
grade = 'C';
else if (mark > 59 && mark < 70)
grade = 'D';
else
grade = 'E';

If you can show me how to use a switch statement for this, please do.
I just don't see how it can be possible, because if the syntax is like this:
switch(choice)
{
case 1: //do stuff; break;
default: //do stuff; break;
}
how can that validate a grade?

**d21998** · 05-20-2002

Thank You everyone. Will the last one enable a loop? I'm not familiar with looping? Also How would I incorporate a 2 digit student ID?

**UnclePunker** · 05-20-2002

This is my interpretation of what you asked, I am a beginner myself, loops depend on a condition you put in the parantheses, a while loop checks the condition before it enter the loop and executes the statements, in this case it executes the program while the variable yesno is not equal to 'n' or 'N' so when it equals something else it exits the loop, the for loop uses the integer variable count gives it a starting point (0) and an end point (0) and how much to count up by each time the loop goes round in this case ++ which means add 1, within my loop it has -- which takes 1 off the count so the loop will execute again, I hope this helps, I can understand if it doesn't and I apologise if I have confused you further.

Code:

#include <iostream.h>

void main()
{
	 int id, count;
	 float mark;
	 char yesno;

	 while (yesno!='n'&&yesno!='N')
	 {
		  cout<<"Please enter student id: ";
		  cin>>id;
		  cout<<"\n\n";

		  cout<<"Please enter student mark: ";
		  for (count=0; count<=0; count++)
		  {
				cin>>mark;

				if (mark<=-1||mark>=101)
				{
					 cout<<"error, re-enter";
					 count--;
				}
		  }

		  cout<<"\n\n";

		  if (mark>=90&&mark<=100)
		  {
				cout<<"Student "<<id<<" got a grade A";
		  }

		  if (mark>=80&&mark<=89)
		  {
				cout<<"Student "<<id<< " got a grade B";
		  }

		  if (mark>=70&&mark<=79)
		  {
				cout<<"Student "<<id<< " got a grade C";
		  }

		  if (mark>=60&&mark<=69)
		  {
				cout<<"Student "<<id<< " got a grade D";
		  }

		  if (mark>=0&&mark<=59)
		  {
				cout<<"Student "<<id<< " got a grade F";
		  }

		  cout<<"\n\n";
		  cout<<"Again?: ";
		  cin>>yesno;
		  cout<<"\n\n";
	 }
	 cout<<"Thankyou Bye";
}

**d21998** · 05-20-2002

Man that program is beautiful, I'm loving C++, I'm learning a lot from you guys on the board. Thank you all very much, especially UnclePunker.

**Mario** · 05-20-2002

Originally posted by tudehopet
I just don't see how it can be possible, because if the syntax is like this:
switch(choice)
{
case 1: //do stuff; break;
default: //do stuff; break;
}
how can that validate a grade?

You are right, it can't.
It took me a while to reply because to be honest I made it a task to find a way to support my statement. But the fact is that I couldn't.

Once again I thought in VB terms and didn't realize the case statement can only accept a constant, instead of the expression i'm so used to. Have to get rid of my last 6 years

Sorry if i mislead you d21998.

**Prelude** · 05-20-2002

>void main()
This is very wrong, main returns an int and anything else is undefined. This is better:

Code:

#include <iostream>
#include <cctype>
using std::cin;
using std::cout;

int main()
{
  int id, mark = 0;
  char yesno = 'y';

  do {
    do {
      cout<<"Please enter student id: ";
      cin>>id;
      cout<<"Please enter student mark: ";
      cin>>mark;
    } while ( mark < 0 && 100 > mark );

    if (mark>=90)
      cout<<"Student "<<id<<" got a grade A\n";
    else if (mark>=80&&mark<=89)
      cout<<"Student "<<id<< " got a grade B\n";
    else if (mark>=70&&mark<=79)
      cout<<"Student "<<id<< " got a grade C\n";
    else if (mark>=60&&mark<=69)
      cout<<"Student "<<id<< " got a grade D\n";
    else if (mark<=59)
      cout<<"Student "<<id<< " got a grade F\n";

    cout<<"Again?: ";
    cin>>yesno;
  } while (toupper(yesno)!='N');
  cout<<"Thank you. Bye\n";
  return 0;
}

>You are right, it can't.
A switch can validate ranges, but you don't want to do it. An if..else if series is far far better than this:

Code:

switch ( mark ) {
case 100:
case 99:
case 98:
case 97:
.
.
.
case 90:
  cout<<"Student "<<id<<" got a grade A\n";
  break;
.
.
.
}

-Prelude

**NANO** · 05-20-2002

I hope that every student get an " A"

Code:

  for (int i= 1; i<= numbers_of_students; i++){
          cout<< "this student got an:eek: :eek: :eek:  A :eek: :eek: :eek: \n";
          cout<< ":D marry X-man:D "<< endl;
  }

Why not????

**Mario** · 05-20-2002

Indulgent!

**skipper** · 05-20-2002

A final indulgence?:

Code:

#include <iostream>
#include <cctype>
using std::cin;
using std::cout;

int main()
{
  int id, mark = 0;
  char yesno = 'y';

  do {
    do {
      cout<<"Please enter student id: ";
      cin>>id;
      cout<<"Please enter student mark: ";
      cin>>mark;
    } while ( mark < 0 && 100 > mark );

    if (mark>=90)
      cout<<"Student "<<id<<" got a grade A\n";
    else if (mark>=80&&mark<=89)
      cout<<"Student "<<id<< " got a grade B\n";
    else if (mark>=70&&mark<=79)
      cout<<"Student "<<id<< " got a grade C\n";
    else if (mark>=60&&mark<=69)
      cout<<"Student "<<id<< " got a grade D\n";
    //else if (mark<=59)  // Not necessary to compare (big deal!)
    else
        cout<<"Student "<<id<< " got a grade F\n";

    cout<<"Again?: ";
    cin>>yesno;
  } while (toupper(yesno)!='N');
  cout<<"Thank you. Bye\n";
  return 0;
}

Very cool, folks!

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