Advanced Coding & Software Engineering Program

Strings in C++ – Complete Tutorial

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Last Updated on: 10th Dec 2025 17:21:47 PM

In programming, handling text such as names, messages, passwords, sentences, and paragraphs is very common. Strings are used in C++ to store and manipulate textual data efficiently.

 

C++ provides two different ways to work with strings:

1. Character Arrays (C-style strings)

2. string class (C++ Standard Library)

 

Understanding both is very important for academic exams, interviews, and real-world applications.

 

What is a String in C++ ?

A string in C++ is a sequence of characters used to represent textual data such as words, sentences, or paragraphs.

 

 Key Characteristics 

• Stores multiple characters

• Ends with a null character ('\0') in C-style strings

• Can be manipulated using built-in functions

• Used for text processing

 

Why Strings Are Needed

Without strings:

• Handling text becomes complex

• Each character must be stored separately

• No built-in functions for manipulation

 

Strings are used for:

• User names

• Passwords

• Messages

• File names

• URLs

• Search and text processing

 

Types of Strings in C++

C++ supports two types of strings:

Type	Description
Character Array	Traditional C-style strings
string Class	Modern, flexible, and safe

 

PART-A: Character Array ( C-Style Strings )

 

1. Character Array (C-Style String)

A character array string is an array of characters ending with a null character '\0', which indicates the end of the string.

 

 

Declaration of Character String

Syntax

char str[size];

 

Example 

char name[20];

 

Initialization of Character String

char name[] = "Cplusplus";

 

Memory representation:

C p l u s p l u s \0

 

Important Rule

C-style strings must end with '\0' to mark the end.

 

Input and Output of Character String 

Using  cin 

char name[20];
cin >> name;
cout << name;

 

⚠ Stops input at space

 

Using  cin.getline() 

char name[50];
cin.getline(name, 50);

 

 ✔ Reads full line including spaces 

 

Important Difference: cin vs getline

Feature	cin	getline
Reads spaces	❌ No	✅ Yes
Reads full sentence	❌	✅
Common use	Words	Sentences

 

String Handling Functions ( <cstring> )

Include header:

#include <cstring>

 

Common String Functions

Function	Description
strlen()	Length of string
strcpy()	Copy string
strcat()	Concatenate strings
strcmp()	Compare strings
strlwr()	Convert to lowercase
strupr()	Convert to uppercase

 

Example:  strlen() 

char s[] = "Hello";
cout << strlen(s);   // Output: 5

 

Example:  strcpy() 

char a[10], b[] = "Hi";
strcpy(a, b);
cout << a;

 

Example:  strcmp() 

if (strcmp("abc", "abc") == 0)
    cout << "Equal";

 

Example Program – C-Style String Functions (One Program)

#include <iostream>
#include <cstring>   // Required for string functions
using namespace std;

int main() {
    char str1[50] = "Hello";
    char str2[50] = "World";
    char str3[50];

    // 1. strlen() – find length of string
    cout << "Length of str1 using strlen(): " << strlen(str1) << endl;

    // 2. strcpy() – copy string
    strcpy(str3, str1);
    cout << "After strcpy(), str3: " << str3 << endl;

    // 3. strcat() – concatenate strings
    strcat(str1, " ");
    strcat(str1, str2);
    cout << "After strcat(), str1: " << str1 << endl;

    // 4. strcmp() – compare strings
    if (strcmp(str2, "World") == 0)
        cout << "str2 and \"World\" are equal" << endl;
    else
        cout << "Strings are not equal" << endl;

    // 5. strlwr() – convert to lowercase
    cout << "Lowercase str1: " << strlwr(str1) << endl;

    // 6. strupr() – convert to uppercase
    cout << "Uppercase str2: " << strupr(str2) << endl;

    return 0;
}

 

Output (Expected)

Length of str1 using strlen(): 5
After strcpy(), str3: Hello
After strcat(), str1: Hello World
str2 and "World" are equal
Lowercase str1: hello world
Uppercase str2: WORLD

 

Limitations of Character Strings

1. Fixed size
2. Buffer overflow risk
3. Complex syntax
4. Manual memory handling

 

➡ These issues are solved by string class.

 

PART-B: string Class (C++ Strings)

 

2. string Class in C++

The string class is part of C++ Standard Library that provides a safe, flexible, and easy way to handle strings.

 

Header File

#include <string>

 

Declaration and Initialization

string name;
string city = "Delhi";

 

Input and Output Using string

Using  cin 

string name;
cin >> name;   // Reads single word

 

Using  getline() 

string name;
getline(cin, name);  // Reads full sentence

 

Common String Operations

 

1. Length of String

string s = "Hello";
cout << s.length();

 

2. Concatenation

string a = "Hello";
string b = "World";
cout << a + " " + b;

 

3. Comparison

if (a == b)
    cout << "Equal";

 

4. Accessing Characters

cout << s[0];   // H

 

5. Modify String

s[0] = 'h';

 

Common String Functions (string class)

Function	Purpose
length()	Returns string length
size()	Same as length
append()	Adds text at end
insert()	Insert text at index
erase()	Removes portion
replace()	Replace substring
find()	Find substring index
substr()	Extract substring

 

Example:  find()  and  substr() 

string s = "Programming";
cout << s.find("gram");      // Output: 3
cout << s.substr(3, 4);      // gram

 

Example Program – All String Operations in One C++ Program

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

int main() {
    string s = "Hello";

    cout << "Original String: " << s << endl;

    // 1. length() – find length of string
    cout << "Length using length(): " << s.length() << endl;

    // 2. size() – same as length
    cout << "Length using size(): " << s.size() << endl;

    // 3. append() – add string at the end
    s.append(" World");
    cout << "After append(): " << s << endl;

    // 4. insert() – insert text at specific position
    s.insert(5, ",");
    cout << "After insert(): " << s << endl;

    // 5. erase() – remove part of string
    s.erase(5, 1);   // remove comma
    cout << "After erase(): " << s << endl;

    // 6. replace() – replace substring
    s.replace(6, 5, "C++");
    cout << "After replace(): " << s << endl;

    // 7. find() – find substring position
    int pos = s.find("C++");
    if (pos != string::npos) {
        cout << "'C++' found at position: " << pos << endl;
    }

    // 8. substr() – extract substring
    string sub = s.substr(6, 3);
    cout << "Substring using substr(): " << sub << endl;

    return 0;
}

 

Output (Expected)

Original String: Hello
Length using length(): 5
Length using size(): 5
After append(): Hello World
After insert(): Hello, World
After erase(): Hello World
After replace(): Hello C++
'C++' found at position: 6
Substring using substr(): C++

 

Real-World Applications of Strings

• Login systems

• Searching text

• Chat applications

• File handling

• Web development

• Data validation

 

Difference Between C-Style String and String Class

Feature	C-Style	string class
Null character	Required	Not needed
Size	Fixed	Dynamic
Safety	Low	High
Ease of use	Hard	Easy
Recommended	❌	✅

 

 

Q1. What is a string?

✔ A sequence of characters used to represent text.

Q2. Difference between char array and string?

✔ Char array is fixed and unsafe, string is dynamic and safe.

Q3. Which header file is used for strings?

✔ <string>

Q4. What is null character?

✔ '\0' marks end of C-string.

Q5. What is getline()?

✔ Reads an entire line including spaces.

 

Best Practices

1. Prefer  string  class over char array
2. Use  getline()  for sentences
3. Pass strings by reference for efficiency
4. Avoid hard-coded sizes

 

Conclusion

Strings are one of the most important topics in C++ programming. From simple input handling to complex text processing, strings are everywhere. Mastering C++ string class makes your programs safer, cleaner, and more professional.

 

Keep practicing — you're doing amazing!

Happy Coding!    

 

 

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