C++ Program to implement the use of STL Map:

stlmap.cpp

#include<iostream>
#include<map>

                // Used to store key value pairs. (Eg: To maintain Phone Book )

using namespace std;

int main()
{
    map<string,long long>phonebook;
    cout<<"Choice:\n 1) Adding a entry into phone book.\n 2) Query to retrieve the person's number.";
    int ch;
    long long no;
    string s;
    while(1){
        cout<<"\nEnter your choice...";
        cin>>ch;
        if(ch==1){
            cout<<"\nEnter the name.";
            cin>>s;
            cout<<"Enter the phone number.";
            cin>>no;
            phonebook[s]=no;
        }
        else if(ch==2){
            cout<<"\nEnter the name whose number you want to retrieve.";
            cin>>s;
            cout<<"The phone number is."<<phonebook[s];
        }
        else{
            break;
        }
    }

    return 0;
}