🔴 Advanced · Lesson 54

Vector in C++ STL

What is Vector in C++ STL?

Vector in C++ STL
A vector is a dynamic array that can grow or shrink at runtime. It supports fast indexing and easy insertion at the end.

Level
🔴 STL, Modern C++ and Projects

Example File
vector.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
vector	Vector used in Vector in C++ STL programming.
push_back	Push_back used in Vector in C++ STL programming.
size	Size used in Vector in C++ STL programming.
index	Index used in Vector in C++ STL programming.
dynamic array	Dynamic array used in Vector in C++ STL programming.

Syntax / Pattern

vector<int> v; v.push_back(value);

Example Program

#include <iostream>
#include <vector>
using namespace std;
int main(){
    vector<int> marks;
    marks.push_back(90);
    marks.push_back(85);
    cout << marks.size();
}

Expected Output

Program Explanation

push_back adds values at the end.
size() returns number of elements.

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?

marks list
dynamic records
algorithm practice

Common Mistakes

Accessing invalid index.
Using vector without #include <vector>.

Practice Tasks

Store five marks in vector and find total.
Remove last element using pop_back().

Summary

Vector in C++ 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.