Explore the full potential of C++ by mastering the standard library.

Become a C++ Programmer

The C++ standard library is a collection of all the tools and utilities available in C++. It received its latest update in 2017, known as C++17. The update introduces many new features that further optimize our code. This module will help us fully grasp C++ and use it to its full potential.

C++ Standard Library

The number of elements a string has (`str.size()`) is in general smaller than the number of elements for which space is reserved: `str.capacity()`. Therefore if we add elements to a string, new memory will not necessarily be allocated. `std:max_size()` return the maximum amount of  elements a string can have. For the three methods the following relation holds: `str.size() <= str.capacity() <= str.max_size()`. 

The following table shows the methods for dealing with memory management of strings.

| **Methods** | **Description** | 
|-|-|
| `str.empty()` | Checks if `str` has elements. |
| `str.size(), str.length()` | Number of elements of the `str`. |
| `str.capacity()` | Number of elements `str` can have without reallocation. | 
| `str.max_size()` |  Number of elements `str` can maximal have. | 
| `str.resize(n)` | Increases `str` to n elements. |  
| `str.reserve(n)` | Reserves memory for a least `n` elements. |
| `str.shrink_to_fit()` | Adjusts the capacity of the string to it's size. | 

The request `str.shrink_to_fit()` is, as in the case of [std::vector](https://www.educative.io/courses/cpp-fundamentals-for-professionals/vectors), non-binding. 

We'll test and alter the capacity of a string.

Size versus Capacity