an option at the end of this prog to ask if I want to run again

I am wanting to put an option at the end of this prog to ask if I want to run again or exit how would i go about doing this
i have already tried this below
Thanks for your help
This is what i tried
((((
std::cout<<"\nall done?";

bool yn;

std::cin>>yn;
if (yn==n)
goto z;

else if

return 0;
}




Start of real prog!!!!!!!


#include<iostream>
int main()

{
z:
int area, volume, height, width, length, sphere, circ, vols, pi, y, n ;

pi = 3.14159265;

std::cout<<"\nDo you wish to calculate Area or Volume or vol of Sphere?(A/V/S)";

char avs;

std::cin>>avs;

if (avs == 'a')
{
//input and calculate area
std::cout<<"\ninput width in inches:";
std::cin>>width;
std::cout<<"\ninput length in inches:";
std::cin>>length;
area=length*width;
std::cout<<"\narea is:";
std::cout<<area;
std::cout<<" Square Inches";
}


else if (avs == 'v')
{
//input and calculate volume
std::cout<<"\ninput width in inches:";
std::cin>>width;
std::cout<<"\ninput height in inches:";
std::cin>>height;
std::cout<<"\ninput length in inches:";
std::cin>>length;
volume=height*width*length;
std::cout<<"\nvolume is:";
std::cout<<volume;
std::cout<< " Cubic Inches";
}

else if (avs == 's')

{ //input and calculate circumfrence
std::cout<<"\n input diameter/2 or radius";
std::cin>>sphere;
vols = 4*pi*(sphere*sphere);
circ = (2*sphere)*pi;
std::cout<<"\narea is:";
std::cout<<vols;
std::cout<< "Cubic inches";
std::cout<<"\nby the way the circumfrence is";
std::cout<<circ;
std::cout<< " Inches";
}

return 0;

}

first of here is how the part that asks if he wants to restart should be written:

Code:

---

              std::cout<<"\nall done?";

              char yn;

              std::cin>>yn;
              if (yn=='n' || yn == 'N')
              goto z;

              else

              return 0;

---

second the use of goto is not advisable, it generally thought of to be a bad thing in C++. A better way to write you program would be something like this:

Code:

---

#include<iostream>
int main()

{
        int area, volume, height, width, length, sphere, circ, vols, pi, y, n ;
       
        bool finished = true; // ADDED THIS: will hold true if finished else it will hold false
        char temp = '\0';          // Used for user input, set to empty.

        pi = 3.14159265;
       
        do
        {
                std::cout<<"\nDo you wish to calculate Area or Volume or vol of Sphere?(A/V/S)";

                char avs;

                std::cin>>avs;

                if (avs == 'a')
                {
                        //input and calculate area
                        std::cout<<"\ninput width in inches:";
                        std::cin>>width;
                        std::cout<<"\ninput length in inches:";
                        std::cin>>length;
                        area=length*width;
                        std::cout<<"\narea is:";
                        std::cout<<area;
                        std::cout<<" Square Inches";
                }


                else if (avs == 'v')
                {
                        //input and calculate volume
                        std::cout<<"\ninput width in inches:";
                        std::cin>>width;
                        std::cout<<"\ninput height in inches:";
                        std::cin>>height;
                        std::cout<<"\ninput length in inches:";
                        std::cin>>length;
                        volume=height*width*length;
                        std::cout<<"\nvolume is:";
                        std::cout<<volume;
                        std::cout<< " Cubic Inches";
                }

                else if (avs == 's')

                { //input and calculate circumfrence
                        std::cout<<"\n input diameter/2 or radius";
                        std::cin>>sphere;
                        vols = 4*pi*(sphere*sphere);
                        circ = (2*sphere)*pi;
                        std::cout<<"\narea is:";
                        std::cout<<vols;
                        std::cout<< "Cubic inches";
                        std::cout<<"\nby the way the circumfrence is";
                        std::cout<<circ;
                        std::cout<< " Inches";
                }
               
                // Does the user wish to continue or quit?
                cout << "Do you want to quit? (Y)es or (N)o?";
                cin >> temp;
               
                if(temp == 'n' || temp == 'N')
                        done = false;
                else if(temp == 'y' || temp == 'Y')
                        done = true;
                else
                {
                        cout << "Invalid Input...";
                        return 0;
                }
        } while(!done)
               
        return 0;
               

}

---

further more, i didn't do it in the above code, but always initialize your variables when you create them.

coverd many times, search it. Very quick way:

Code:

---

#include<iostream>
#include<ctype.h>

using namespace std;

const char EXIT = 'Y';

int main()

{
z:
int area, volume, height, width, length, sphere, circ, vols, pi, y, n ;

pi = 3.14159265;

char prompt;

cout << "enter 'y' to run (again): ";
cin >> prompt;

prompt = toupper(prompt);

do
{
std::cout<<"\nDo you wish to calculate Area or Volume or vol of Sphere?(A/V/S)";

char avs;

std::cin>>avs;

if (avs == 'a')
{
//input and calculate area
std::cout<<"\ninput width in inches:";
std::cin>>width;
std::cout<<"\ninput length in inches:";
std::cin>>length;
area=length*width;
std::cout<<"\narea is:";
std::cout<<area;
std::cout<<" Square Inches";
}


else if (avs == 'v')
{
//input and calculate volume
std::cout<<"\ninput width in inches:";
std::cin>>width;
std::cout<<"\ninput height in inches:";
std::cin>>height;
std::cout<<"\ninput length in inches:";
std::cin>>length;
volume=height*width*length;
std::cout<<"\nvolume is:";
std::cout<<volume;
std::cout<< " Cubic Inches";
}

else if (avs == 's')

{ //input and calculate circumfrence
std::cout<<"\n input diameter/2 or radius";
std::cin>>sphere;
vols = 4*pi*(sphere*sphere);
circ = (2*sphere)*pi;
std::cout<<"\narea is:";
std::cout<<vols;
std::cout<< "Cubic inches";
std::cout<<"\nby the way the circumfrence is";
std::cout<<circ;
std::cout<< " Inches";
}
}while (prompt = EXIT);



return 0;

}

---