Stack

stack-is an abstract data type and data structure based on the principle of Last In First Out (LIFO). Stacks are used extensively at every level of a modern computer system. For example, a modern PC uses stacks at the architecture level, which are used in the basic design of an operating system for interrupt handling and operating system function calls. Among other uses, stacks are used to run a Java Virtual Machine, and the Java language itself has a class called "Stack", which can be used by the programmer. The stack is ubiquitous.A stack is a homogeneous collection of items of any one type, arranged linearly with access at one end only, called the top. This means that data can be added or removed from only the top. Formally this type of stack is called a Last In, First Out (LIFO) stack. Data is added to the stack using the Push operation, and removed using the Pop operation.
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Reference:http://en.wikipedia.org/wiki/Stack_(data_structure)
http://www.cs.usask.ca/content/resources/tutorials/csconcepts/1998_5/stacks/1-1.html