The Standard Template Library (STL) is a set of C++ template classes and functions to provide common programming using data structures and functions such as lists, stacks, arrays, etc. STL is a library consisting of container classes, algorithms, and iterators. It is a generalized library and so, its components are parameterized. A working knowledge of template classes is a prerequisite for working with STL. STL is an acronym for standard template library. It is a set of C++ template classes that provide generic classes and function that can be used to implement data structures and algorithms .STL is mainly composed of : 1. Algorithms 2. Containers 3. Iterators