Hi everyone, I was wondering if anyone could help me figure out this issue I am having with a program I have written. The problem is after you type in the number of days you want to rent the car for if it is less than 0 or greater than 30 it is supposed to loop back to What class of car do you want and give an message such as invalid entry. I have tried all type of loops, while loops, do while loops if, if , and I still cannot figure it out the program is written below. Thanks in advance for your help it has been kicking my butt. John

#include <iostream>
#include <cmath>
#include <string>
using namespace std;
int main (){

    cout.setf(std::ios_base::fixed);   // Using precision function to limit decimal output to 2
    cout.setf(std::ios_base::showpoint);
    cout.precision(2);




    char carType = 0;   //  character type will be car type selected
    int days = (0 <= 30);


    cout << "Welcome to the Car Rental Program.\n";

    do {

        cout << "What class of car do you want (A, B, C, or D)? ";  // Asking user what type of car they would like to choose.
        cin >> carType;   // User enters car type
        switch (carType){
        case 'a':
        case 'A':
            cout << "How many days will you keep the car (no more than 30 days)? ";  // Asking user number of days car is needed
            cin >> days;
            cout << "Your price will be $" << 30*days*1.06 << ". Is this OK (Y or N)?";
            cin >> carType;
            break;
        case 'b':
        case 'B':
            cout << "How many days will you keep the car (no more than 30 days)? ";
            cin >> days;
            cout << "Your price will be $" << 40*days*1.06 << ". Is this OK (Y or N)?";
            cin >> carType;
            break;
        case 'c':
        case 'C':
            cout << "How many days will you keep the car (no more than 30 days)? ";
            cin >> days;
            cout << "Your price will be $" << 55*days*1.06 << ". Is this OK (Y or N)?";
            cin >> carType;
            break;
        case 'd':
        case 'D':
            cout << "How many days will you keep the car (no more than 30 days)? ";
            cin >> days;
            cout << "Your price will be $" << 80*days*1.06 << ". Is this OK (Y or N)?";
            cin >> carType;
            break;
        default :
            cout << "Invalid Entry please try again." << carType<< "\n"; // If user selects character other than a, b, c, d, in lower case or caps will get error message
        }
    }   while (carType !='Y' && carType != 'y');  // if user chooses Y they will get a thank you message can either be caps or lower case.

        cout << "Thank You!";


    return 0;
}

Thanks again for all the help,

John

Please use code tags, and all of the "text" in the switch statement is not needed. You just need to change the amount within the switch. you also have a few unneeded headers. Also, your decimal allocation code is a bit long, and you can shorten that up to one line.

As for adding a loop, a simple do-while loop would suffice.

Here is your code with these corrections implemented. Please take the time to figure out the changes I made, as they were quite simple, but important/effective. =]

#include <iostream>
#include <iomanip>
using namespace std;
int main (){
	cout << fixed << setprecision(2); // Using precision function to limit decimal output to 2
	char carType; // character type will be car type selected
	int days, amount;
	cout << "Welcome to the Car Rental Program.\n";
	do {
		cout << "What class of car do you want (A, B, C, or D)? "; // Asking user what type of car they would like to choose.
		cin >> carType; // User enters car type
		switch (carType){
case 'a':
case 'A':
	amount = 30;
	break;
case 'b':
case 'B':
	amount = 40;
	break;
case 'c':
case 'C':
	amount = 55;
	break;
case 'd':
case 'D':
	amount = 80;
	break;
default :
	cout << "Invalid Entry please try again." << carType << "\n"; // If user selects character other than a, b, c, d, in lower case or caps will get error message
		}
		do{
		cout << "How many days will you keep the car (no more than 30 days)? ";
		cin >> days;
		}while(days > 30 || days < 1);
		cout << "Your price will be $" << amount*days*1.06 << ". Is this OK (Y or N)?";
		cin >> carType;
	}while (carType !='Y' && carType != 'y'); // if user chooses Y they will get a thank you message can either be caps or lower case.
	cout << "Thank You!\n\n";
	return 0;
}
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