C++ program to implement a string class and make use of operator overloading:

StringClass.cpp

#include<iostream>
#include<cstring>

using namespace std;

class sstring{
    char* s;
    int len;
    public:
        sstring();
        sstring operator +(sstring a);
        sstring operator -(sstring a);
        bool operator ==(sstring a);
        bool operator >(sstring a);
        bool operator <(sstring a);
        friend istream& operator >>(istream &inp,sstring &a){
            char x[100];
            inp>>x;
            a.len=strlen(x);
            a.s=new char[a.len+1];
            strcpy(a.s,x);
            return inp;
        }
        friend ostream& operator <<(ostream &out,sstring &a){
            out<<a.s<<endl;
            return out;
        }
};


sstring::sstring(){
    len=0;
    s=new char[len+1];
}

sstring sstring::operator+(sstring a){
    sstring t;
    t.len=len+a.len;
    t.s=new char[t.len+1];
    strcpy(t.s,s);
    strcat(t.s," ");
    strcat(t.s,a.s);
    return t;
}

sstring sstring::operator-(sstring a){
    sstring t;
    int x,y,i,j,k;
    int flag,ok=0;
    for(i=0;i<len-a.len;i++){
        flag=0;
        k=0;
        for(j=i;j<i+a.len;j++){
            if(s[j]!=a.s[k++]){
                flag=1;
            }
        }
        if(flag==0){
            x=i;
            y=i+a.len-1;
            ok=1;
            break;
        }
    }
    if(ok==0){
        cout<<"Substring not found\n";
        return *this;
    }
    t.len=len-a.len;
    t.s=new char[t.len+1];
    j=0;
    for(i=0;i<len;i++){
        if(i<x || i>y){
            t.s[j++]=s[i];
        }
    }
    t.s[j]='\0';
    return t;
}

bool sstring::operator ==(sstring a){
    if(strcmp(s,a.s)==0)return true;
    else return false;
}

bool sstring::operator<(sstring a){
    if(strcmp(s,a.s)<0)return true;
    else return false;
}

bool sstring::operator>(sstring a){
    if(strcmp(s,a.s)>0)return true;
    else return false;
}

int main()
{
    int ch;
    cout<<"Choice: 1) Concatenation 2) String Deletion 3) String Compare 3) Exit";

    sstring a,b,c;
    while(1){
        cout<<"\nEnter your choice..";
        cin>>ch;
        if(ch==1){
            cout<<"Enter the first string ";
            cin>>a;
            cout<<"Enter the second string ";
            cin>>b;
            c=a+b;
            cout<<"\nThe concatenation of the given two strings is "<<c;
        }
        else if(ch==2){
            cout<<"Enter the string ";
            cin>>a;
            cout<<"Enter the substring to be deleted ";
            cin>>b;
            c=a-b;
            cout<<"\nThe resultant string is "<<c;
        }
        else if(ch==3){
            cout<<"Enter the first string ";
            cin>>a;
            cout<<"Enter the second string ";
            cin>>b;
            if(a==b){
                cout<<"The given two strings are equal.";
            }
            else if(a>b){
                cout<<"The first string is greater than the second string.";
            }
            else if(a<b){
                cout<<"The first string is lesser than the second string.";
            }
        }
        else{
            break;
        }
    }
    return 0;
}