The C++ Standard Template Library (STL)
- Difficulty Level : Easy
- Last Updated : 15 Jul, 2022
The Standard Template Library (STL) is a set of C++ template classes to provide common programming data structures and functions such as lists, stacks, arrays, etc. It is a library of container classes, algorithms, and iterators. It is a generalized library and so, its components are parameterized. Working knowledge of template classes is a prerequisite for working with STL.
STL has 4 components:
- Algorithms
- Containers
- Functions
- Iterators
Algorithms
The header algorithm defines a collection of functions specially designed to be used on a range of elements. They act on containers and provide means for various operations for the contents of the containers.
- Algorithm
- Numeric
Containers
Containers or container classes store objects and data. There are in total seven standards “first-class” container classes and three container adaptor classes and only seven header files that provide access to these containers or container adaptors.
- Sequence Containers: implement data structures that can be accessed in a sequential manner.
- vector
- list
- deque
- arrays
- forward_list( Introduced in C++11)
- Container Adaptors: provide a different interface for sequential containers.
- Associative Containers: implement sorted data structures that can be quickly searched (O(log n) complexity).
- Unordered Associative Containers: implement unordered data structures that can be quickly searched
- unordered_set (Introduced in C++11)
- unordered_multiset (Introduced in C++11)
- unordered_map (Introduced in C++11)
- unordered_multimap (Introduced in C++11)


Functions
The STL includes classes that overload the function call operator. Instances of such classes are called function objects or functors. Functors allow the working of the associated function to be customized with the help of parameters to be passed.
Iterators
As the name suggests, iterators are used for working upon a sequence of values. They are the major feature that allows generality in STL.
Utility Library
Defined in header <utility>.
To master C++ Standard Template Library (STL) in the most efficient and effective way, do check out this C++ STL Online Course by GeeksforGeeks. The course covers the basics of C++ and in-depth explanations to all C++ STL containers, iterators, etc along with video explanations of a few problems. Also, you’ll learn to use STL inbuilt classes and functions in order to implement some of the complex data structures and perform operations on them conveniently.
Please write comments if you find anything incorrect, or if you want to share more information about the topic discussed above.