STL

STL (Standard Template Library) is a software library initially designed by Alexander Stepanov and Meng Lee in the early 1990s. It was later adopted into the C++ Standard Library. STL provides a set of common data structures and algorithms that can be used with any built-in or user-defined type that satisfies certain requirements.

The core components of the STL include:

- Containers: These are data structures that store collections of objects. They are divided into sequence containers (such as vector, list, and deque), associative containers (such as set, multiset, map, and multimap), and unordered associative containers (such as unordered_set, unordered_multiset, unordered_map, and unordered_multimap).

- Algorithms: STL provides a set of algorithms for operations such as searching, sorting, counting, manipulating, and others. These algorithms are generic and can work with any container or directly on sequences of elements.

- Iterators: Iterators are objects that point to elements within containers. They are used to traverse the elements in a container. STL iterators are categorized into five types based on their capabilities: input iterators, output iterators, forward iterators, bidirectional iterators, and random access iterators.

- Function objects: Also known as functors, these are objects that can be called as if they were ordinary functions. They are used in STL for defining operations to be performed by algorithms, such as comparisons and arithmetic operations.

- Adaptors: These modify a container or function object's interface for a specific purpose. Examples include stack, queue, and priority_queue for containers, and bind, function, and not1 for function objects.

STL has had a significant impact on the development of C++ and is widely used in software engineering for its efficiency and flexibility. It allows developers to focus on higher-level aspects of their programs without having to reinvent common data structures and algorithms.