Simple Contact Book in C++ Using map and File I/O

This project is a stripped-down version of a contact book, great for beginners. We’ll use a map to store contacts (name → number) and simple file I/O to save and load data.

Simple Contact Book in C++ Using map and File I/O

What This Program Does

• Adds new contacts

• Displays all contacts

• Saves contacts to a text file

• Loads contacts at startup

#include <iostream>
#include <map>
#include <fstream>
using namespace std;

map<string, string> contacts;

void saveToFile() {
    ofstream outFile("contacts.txt");
    map<string, string>::iterator it;
    for (it = contacts.begin(); it != contacts.end(); it++) {
        outFile << it->first << "," << it->second << endl;
    }
    outFile.close();
}

void loadFromFile() {
    ifstream inFile("contacts.txt");
    string line,name,number;
    while (getline(inFile,line)){
        int pos = line.find(',');
        if (pos != string::npos) {
            name = line.substr(0, pos);
            number = line.substr(pos + 1);
            contacts[name] = number;
        }
    }
    inFile.close();
}

void showContacts() {
    cout << "---- Contact List ----" << endl;
    map<string, string>::iterator it;
    for (it = contacts.begin(); it != contacts.end(); it++) {
        cout << it->first << ": " << it->second << endl;
    }
}

int main() {
    loadFromFile();
    contacts["Alice"] = "9876543210";
    contacts["Bob"] = "9123456780";
    saveToFile();
    showContacts();

    return 0;
}

Output:
---- Contact List ----
Alice: 9876543210
Bob: 9123456780