Help with looping program

[campurdy]

Hello,
I am currently working on a question presented in my homework as follows:

---Modify last week’s area of triangle program so that it loops until valid, usable input is provided.


Here is my code from the previous problem that I am trying to loop.

  #include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;

int main()
{
    double a,b,c,area,sum,total,newtotal;
    cout<<"This program is used to calculate the area of a heronian triangle" "\n";
    cout<<"when user inputs a rational number." "\n\n\n";
    cout<<"input length a in meters""\n";
    cin>>a;
    if(cin.fail())
    cout<<"Please input a number instead."<<endl;
    cout<<"input length b in meters""\n";
    cin>>b;
    if(cin.fail())
    cout<<"Please input a number instead."<<endl;
    cout<<"input length c in meters""\n";
    cin>>c;
    if(cin.fail())
    cout<<"Please input a number instead."<<endl;
    if(sqrt(pow(a,2)+pow(b,2))>=c){
    sum=a+b+c;
    total = sum/2;
    newtotal = total*(total-a)*(total-b)*(total-c);
    newtotal = sqrt(newtotal);
    cout<<"The given heronian triangle has an area of "<<newtotal<<"M^2""\n\n";
    }else{
    cout<<"Invalid dimensions were entered. Please check dimensions and try again\n";
}
   
    
    
    system ("PAUSE");
    return 0;
    

}

The lines I have bolded with 'cin.fail' are where I have started working on my program. So far it seems to be coming along as now where I input a value other than an integer, I receive my message "Please input a number instead". I am still having a few problems though.

1) I am still having my program try to solve for the non-integer input as 'a'
Is there something I can do to stop this from happening?
Also the program is outputting "Please input a number instead" for all instances a, b, and c when I have only input a non-int for a. Is there an easy way to fix this as well that I'm just skipping over?

2) I am unsure where to start on how to loop my program. Would a 'while' loop be the best way to do this or possibly a 'do-while'?


Sorry for the multiple questions, I am just having a hard time grasping the concept of adding loops into my programs.
Any help would be appreciated, along with a visual possibly of information given as being early on I find it hard to put some things together.

Thanks in advance,
Cameron

[keskiverto]

http://www.cplusplus.com/doc/tutorial/control/#loops

[campurdy]

I found the link to be very beneficial.
I will include a finished copy after using the information you provided.

Thank you Keskiverto