🔴 Advanced · Lesson 53

Standard Template Library (STL)

What is Standard Template Library (STL)?

Standard Template Library (STL)
STL is a powerful C++ library containing containers, iterators, algorithms and function objects. It helps write shorter and efficient programs.

Level
🔴 STL, Modern C++ and Projects

Example File
stl-introduction.cpp

Main Focus
Concept + syntax + practical C++ program

Why should you learn this?

It helps you write correct and readable C++ programs.
It is used repeatedly in school practicals, projects and competitive programming.
It builds the base for advanced topics such as OOP, STL and data structures.

Important Terms

Term	Meaning / Use
container	Container used in Standard Template Library (STL) programming.
iterator	Iterator used in Standard Template Library (STL) programming.
algorithm	Algorithm used in Standard Template Library (STL) programming.
vector	Vector used in Standard Template Library (STL) programming.
map	Map used in Standard Template Library (STL) programming.

Syntax / Pattern

Use containers like vector, set, map and algorithms like sort().

Example Program

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
    vector<int> v = {3,1,2};
    sort(v.begin(), v.end());
    for(int x : v) cout << x << " ";
}

Expected Output

1 2 3

Program Explanation

vector stores numbers.
sort() arranges them in ascending order.

Exam Tip: In C++ practical answers, write the logic first, then the program, then expected output. For theory, always include one suitable example.

Where will you use it?

competitive programming
data processing
fast development

Common Mistakes

Reinventing common data structures unnecessarily.
Using algorithm without including correct header.

Practice Tasks

List four STL containers.
Sort marks using vector.

Summary

Standard Template Library (STL) is an important C++ topic. Learn the definition, understand the syntax, run the example program and then solve the practice tasks to make the concept strong.