challenging program

/*
*
Challenging C++ program VNSGU(MCA)
Create a class HugeInteger that uses a 40-element array of digits to store integers as large as 40-digits each.Provide member methods inputHugeInteger, outputHugeInteger, addHugeIntegers and substractHugeIntegers. For comparing HugeInteger objects, provide methods isEqualTo, isNotEqualTo,isGreaterThan, isLessThan, IsGreaterThanOrEqualTo and isLessThanOrEqualTo--each of these is a
“predicate” method that simply returns true if the relationship holds between the two huge integers and returns
false if the relationship does not hold. Also provide a predicate method isZero.

*/
#include<iostream>
using namespace std;
class HugeInteger
{
    string num;
    int no[40];
    int l;
    public:
        void inputHugeInteger()
        {
            cout<<"\n Enter no=";
            cin>>num;
            if(num.length()>40)
            {
                cout<<"\n Number is not more than 40 digits";
            }
            else
            {
                convert_str_to_num(num);//this method convert str to num
            }
        }

        void convert_str_to_num(string s)
        {
            l=s.length();
            for(int k=0;k<l;k++)
            {
                no[k]=s[k]-'0';//convert char to int
            }
        }

        void outputHugeInteger()
        {
            cout<<"\n";
            for(int k=0;k<l;k++)
            {
                cout<<no[k];
            }
        }

        bool is_zero()
        {
            int flag=1;
            for(int k=0;k<l;k++)
            {
                if(no[k]!=0)
                {
                    flag=0;
                    break;
                }
            }
            if(flag==1)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        bool isEqualTo(HugeInteger temp)
        {
            int flag=1;
            if(l==temp.l)
            {
                for(int k=0;k<l;k++)
                {
                    if(no[k]!=temp.no[k])
                    {
                        flag=0;
                        break;
                    }
                }
            }
            else
            {
                flag=0;
            }
            if(flag==1)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        bool isNotEqualTo(HugeInteger temp)
        {
            isEqualTo(temp)?cout<<"False":cout<<"True";
        }
        bool isgreaterthan(HugeInteger temp)
        {
            int flag=0;
            int d;
            if(l!=temp.l)
            {
                d=l-temp.l;
                if(d < 0)
                {
                    flag=1;
                }
            }
            else
            {
                for(int k=0;k<l;k++)
                {
                    if(no[k] < temp.no[k])
                    {
                        flag=1;
                        break;
                    }
                }
            }
            if(flag==1)
            {
                return false;
            }
            else
            {
                if(isEqualTo(temp)==0)
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
        }
        bool islessthan(HugeInteger temp)
        {
            int flag=0;
            int d;
            if(l!=temp.l)
            {
                d=l-temp.l;
                if(d < 0)
                {
                    flag=1;
                }
            }
            else
            {
                for(int k=0;k<l;k++)
                {
                    if(no[k] < temp.no[k])
                    {
                        flag=1;
                        break;
                    }
                }
            }
            if(flag==1)
            {
                return true;
            }
            else
            {
                if(isEqualTo(temp)==0)
                {
                    return true;
                }
                else
                {
                    return false;
                }
            }
        }
        bool isgreaterthanequalto(HugeInteger temp)
        {
            if(isEqualTo(temp)==1)
            {
                return true;
            }
            else
            {
                return true;
            }
        }
        bool islessthanequalto(HugeInteger temp)
        {
            if(isEqualTo(temp)==0)
            {
                return true;
            }
            else
            {
                return true;
            }
        }

        void addHugeIntegers(HugeInteger temp)
        {
            int sum[40];
            int s,flag=0;
            int t=0;
            int size1=num.length();
            int size2=temp.num.length();
            if(size1-size2==0)
            {
                for(int k=size2-1;k>=0;k--)
                {
                    s=no[k]+temp.no[k];
                    if(k==0 && s>=10)
                    {
                        flag=1;
                    }
                    if(s>=10)
                    {
                        sum[k]=s%10;
                        no[k-1]=no[k-1]+s/10;

                    }
                    else
                    {
                        sum[k]=no[k]+temp.no[k];
                    }

                }
                if(flag==1)
                {
                    cout<<1;
                }
                for(int i=0;i<size1;i++)
                {
                    cout<<sum[i];
                }
            }

        }
};
int main()
{
    HugeInteger h1,h2;
    h1.inputHugeInteger();
    h2.inputHugeInteger();
    h1.outputHugeInteger();
    h2.outputHugeInteger();
    cout<<"\n No1 is zero=";
    h1.is_zero()?cout<<"true":cout<<"false";
    cout<<"\n No2 is zero=";
    h2.is_zero()?cout<<"true":cout<<"false";
    cout<<"\n No1 is equal to No2=";
    h1.isEqualTo(h2)?cout<<"true":cout<<"false";
    cout<<"\n No1 is not equal to No2=";
    h1.isNotEqualTo(h2);
    cout<<"\n No1 is greater than No2=";
    h1.isgreaterthan(h2)?cout<<"true":cout<<"false";
    cout<<"\n No1 is greater than equal to No2=";
    h1.isgreaterthanequalto(h2)?cout<<"true":cout<<"false";
    cout<<"\n No1 is less than No2=";
    h1.islessthan(h2)?cout<<"true":cout<<"false";
    cout<<"\n No1 is less than equal to No2=";
    h1.islessthanequalto(h2)?cout<<"true":cout<<"false";
    cout<<"\n Addition of 2 number is ";
    h1.addHugeIntegers(h2);
}