In this shot, we will learn about the **`vector::back()`** function in C++.

#         
#  Introduction
The `vector::back()` function is available in the `<vector>` header file and returns a reference to the last element in the vector. 

If we call the `back()` function on a vector that contains no elements, then we will get a "Segmentation Fault Error."
 

#            
#  Syntax
The syntax of the `vector::back()` function is given below:
```
reference back();
```

#      
## Parameters
The `vector::back()` function does not accept any parameters.


##     
## Return value
`vector::back()` returns a reference that points to the last element of the vector. 

##     
## Code
Let's have a look at the code.

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

int main()
{
  vector<int> vec;

//  cout << " The last element of an empty vector is: " << vec.back();

  vec.push_back(3);
  vec.push_back(4);
  vec.push_back(5);
  vec.push_back(6);
  vec.push_back(2);

  cout << " The last element of the vector is: " << vec.back();

  return 0;
}

#     
## Explanation
* In *line 1*, we include the C++ standard header file for the input-output stream (`iostream`), which is used to read and write from streams.

* In *line 2*, we include the header file for C++ standard `vector`, which includes all the functions and operations related to the vector container.

* In *line 3*, we use the standard (`std`) namespace, which means that we use all the things within the `std` namespace.  

* In *line 7*, we declare the integer type vector container named `vec`.

* In *line 9*, we call the `back()` function on an empty vector. If we uncomment the line, then we will get a "Segmentation Fault Error" because there is no element in the vector.

* In *lines 11 to 15*, we push back the different elements to the vector container `vec`.   

* In *line 17*, we print the result of the function `back()`, which returns the last element of the vector container. In this example, $2$ is the last element, so the output is $2$. 

In this way, we can easily get the last element present in the vector. 



What is the vector.back() function in C++?

The `vector::back()` function returns a reference to the last element in a C++ vector and can cause a segmentation fault if the vector is empty.