What are strings?

String stores text as a character sequence.

• "Hello"
• "C++ Programming"
• "John Doe"

Char holds one letter. String holds many.

Word on paper analogy. Each letter has an index.

H e l l o
0 1 2 3 4

Why do strings exist?

• Reading names
• Displaying messages
• Comparing passwords
• Searching text
• Editing words and sentences

Real-world use cases

• Login systems
• Search engines
• Chat applications
• Text editors
• File processing
• Email validation
• Customer management systems
• Web applications

Including the string library

#include <string>

Declaring a string

string variableName;

string name;

Initializing a string

string language = "C++";

Reading string input

cin stops at first whitespace.

cin >> name;
// Input: John Smith
// Output: John

getline reads the whole line.

getline(cin, name);
// Input: John Smith
// Output: John Smith

Accessing characters

name[0]
name[1]
name[2]

String length

name.length()
name.size()

Both return the character count.

Concatenating strings

+ operator joins two strings.

string fullName = firstName + " " + lastName;

Comparing strings

if (password == "admin")

Modifying strings

Change chars using their index.

name[0] = 'J';

Example 1: Declare and display a string

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string name = "Alice";
    cout << name;

    return 0;
}

Example 2: Read a full name

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string name;

    cout << "Enter your full name: ";
    getline(cin, name);
    cout << "Welcome, " << name;

    return 0;
}

Example 3: String concatenation

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string firstName = "John";
    string lastName = "Doe";
    string fullName = firstName + " " + lastName;

    cout << fullName;

    return 0;
}

Example 4: Count vowels

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string text;
    int vowels = 0;

    cout << "Enter a word: ";
    cin >> text;

    for (int i = 0; i < text.length(); i++)
    {
        char ch = tolower(text[i]);

        if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u')
        {
            vowels++;
        }
    }

    cout << "Number of vowels = " << vowels;

    return 0;
}

Example 5: Password verification

#include <iostream>
#include <string>
using namespace std;

int main()
{
    string password;

    cout << "Enter password: ";
    cin >> password;

    if (password == "admin123")
    {
        cout << "Access Granted";
    }
    else
    {
        cout << "Access Denied";
    }

    return 0;
}

Common mistakes and pitfalls

• cin for full names. Fix: use getline
• Missing string header. Fix: include it
• Invalid index access. Fix: check length first
• Comparing C-strings with ==. Fix: use std::string or strcmp
• Mixing cin and getline. Fix: use cin.ignore() first

// Wrong
string name;
cin >> name;
// Input: John Smith
// Output: John

// Correct
string name;
getline(cin, name);
// Output: John Smith

Best practices

• Prefer std::string over char arrays
• Use getline for names with spaces
• Validate input before processing
• Avoid accessing past string length
• Use clear names like userName
• Use built-in string functions first

When not to use this

• Legacy C libraries need char arrays
• Memory-constrained embedded systems
• Fixed-size binary data, not text

Summary

• Strings store and manage text
• Include string header for std::string
• Strings declare, init, modify, compare easily
• cin stops at space, getline reads full line
• Characters use zero-based indexing
• length or size gives character count
• + operator joins strings
• Prefer std::string in modern code

Frequently asked questions

What is a string in C++?

Character sequence storing text data.

What is the difference between char and string?

Char holds one letter. String holds many.

Why does cin stop reading at spaces?

>> treats space as separator. Use getline instead.

What is the difference between length() and size()?

No real difference. Both count characters.

Why use std::string over a character array?

Safer, easier, auto memory, built-in operations.