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Singly rooted hierarchy
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<p>The singly rooted hierarchy, in <a href="/facts/Object-oriented_programming/TxNMEcao">object-oriented programming</a>, is a characteristic of most (but not all) <a href="/facts/Object-oriented_programming/TxNMEcao">OOP</a>-based <a href="/facts/Programming_language/cWTYbgWa">programming languages</a>. In most such languages, in fact, all classes <a href="/facts/Inheritance_(object-oriented_programming)/a7R1xv8n">inherit</a> directly or indirectly from a single root, usually with a name similar to Object; all classes then form a common inheritance hierarchy. </p><p>This idea was introduced first by <a href="/facts/Smalltalk/Ru2UPVDE">Smalltalk</a>, and was since used in most other object-oriented languages (notably <a href="/facts/Java_(programming_language)/9ScgFyAL">Java</a> and <a href="/facts/C_Sharp_(programming_language)/UC2gxeyb">C#</a>). </p><p>A notable exception is <a href="/facts/C%252B%252B/Et0F2qn9">C++</a>, where (mainly for compatibility with C and efficiency) there is no single object hierarchy. This feature is especially useful for container libraries - they only need to allow putting an Object in a container to allow objects of any class to be put in the container. Containers in C++ have been implemented with <a href="/facts/Multiple_inheritance/kFvNb9rY">multiple inheritance</a>, and with help of <a href="/facts/Template_(programming)/TXEqGy7R">template</a>-based <a href="/facts/Generic_programming/kqtqJk7p">generic programming</a> by <a href="/facts/Bjarne_Stroustrup/Be1Yq6rn">Bjarne Stroustrup</a>. Other object-oriented languages without a singly rooted hierarchy include <a href="/facts/Objective-C/5mM557BW">Objective-C</a> and <a href="/facts/PHP/vU6YRJX0">PHP</a>. </p>