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Stack (abstract data type)
In computer science, a stack is an abstract data type that serves as a collection of elements with two main operations:
Additionally, a peek operation can, without modifying the stack, return the value of the last element added (the item at the top of the stack). The name stack is an analogy to a set of physical items stacked one atop another, such as a stack of plates.
The order in which an element added to or removed from a stack is described as last in, first out, referred to by the acronym LIFO. As with a stack of physical objects, this structure makes it easy to take an item off the top of the stack, but accessing a datum deeper in the stack may require removing multiple other items first.
Considered a sequential collection, a stack has one end which is the only position at which the push and pop operations may occur, the top of the stack, and is fixed at the other end, the bottom. A stack may be implemented as, for example, a singly linked list with a pointer to the top element.
A stack may be implemented to have a bounded capacity. If the stack is full and does not contain enough space to accept another element, the stack is in a state of stack overflow.
Stacks entered the computer science literature in 1946, when Alan Turing used the terms "bury" and "unbury" as a means of calling and returning from subroutines. Subroutines and a two-level stack had already been implemented in Konrad Zuse's Z4 in 1945.
Klaus Samelson and Friedrich L. Bauer of Technical University Munich proposed the idea of a stack called Operationskeller ("operational cellar") in 1955 and filed a patent in 1957. In March 1988, by which time Samelson was deceased, Bauer received the IEEE Computer Pioneer Award for the invention of the stack principle. Similar concepts were independently developed by Charles Leonard Hamblin in the first half of 1954 and by Wilhelm Kämmerer with his automatisches Gedächtnis ("automatic memory") in 1958.
Stacks are often described using the analogy of a spring-loaded stack of plates in a cafeteria. Clean plates are placed on top of the stack, pushing down any plates already there. When the top plate is removed from the stack, the one below it is elevated to become the new top plate.
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Stack (abstract data type) AI simulator
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Stack (abstract data type)
In computer science, a stack is an abstract data type that serves as a collection of elements with two main operations:
Additionally, a peek operation can, without modifying the stack, return the value of the last element added (the item at the top of the stack). The name stack is an analogy to a set of physical items stacked one atop another, such as a stack of plates.
The order in which an element added to or removed from a stack is described as last in, first out, referred to by the acronym LIFO. As with a stack of physical objects, this structure makes it easy to take an item off the top of the stack, but accessing a datum deeper in the stack may require removing multiple other items first.
Considered a sequential collection, a stack has one end which is the only position at which the push and pop operations may occur, the top of the stack, and is fixed at the other end, the bottom. A stack may be implemented as, for example, a singly linked list with a pointer to the top element.
A stack may be implemented to have a bounded capacity. If the stack is full and does not contain enough space to accept another element, the stack is in a state of stack overflow.
Stacks entered the computer science literature in 1946, when Alan Turing used the terms "bury" and "unbury" as a means of calling and returning from subroutines. Subroutines and a two-level stack had already been implemented in Konrad Zuse's Z4 in 1945.
Klaus Samelson and Friedrich L. Bauer of Technical University Munich proposed the idea of a stack called Operationskeller ("operational cellar") in 1955 and filed a patent in 1957. In March 1988, by which time Samelson was deceased, Bauer received the IEEE Computer Pioneer Award for the invention of the stack principle. Similar concepts were independently developed by Charles Leonard Hamblin in the first half of 1954 and by Wilhelm Kämmerer with his automatisches Gedächtnis ("automatic memory") in 1958.
Stacks are often described using the analogy of a spring-loaded stack of plates in a cafeteria. Clean plates are placed on top of the stack, pushing down any plates already there. When the top plate is removed from the stack, the one below it is elevated to become the new top plate.