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The physical level describes complex low-level data structures in detail. Logical level: The next higher level of abstraction describes what data the database stores, and what relationships exist among those data. The logical level thus describes an entire database in terms of a small number of relatively simple structures.
Common data structures and their usage Data Structure Definition Usage Array: A fixed-size collection of elements of the same data type, accessible by indices. General-purpose storage and retrieval, basis of many more complex structures. List: An abstract data type that represents a sequence of values, where the same value may occur more than once.
Container abstract data types include: FIFO queues; LIFO stacks; Priority queues; Lookup tables (LUTs) Key-associated data structures. Sets, containing and indexing objects by value or by specific property; Maps, associating to each key a "value" for lookup; Common data structures used to implement these abstract types include: Arrays and their ...
A data structure known as a hash table.. In computer science, a data structure is a data organization and storage format that is usually chosen for efficient access to data. [1] [2] [3] More precisely, a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data, [4] i.e., it is an algebraic structure about data.
In computer programming, a collection is an abstract data type that is a grouping of items that can be used in a polymorphic way. Often, the items are of the same data type such as int or string. Sometimes the items derive from a common type; even deriving from the most general type of a programming language such as object or variant.
Simple representation of a stack runtime with push and pop operations. In computer science, a stack is an abstract data type that serves as a collection of elements with two main operations: Push, which adds an element to the collection, and; Pop, which removes the most recently added element.
The basic mechanism of control abstraction is a function or subroutine. Data abstractions include various forms of type polymorphism. More elaborate mechanisms that may combine data and control abstractions include: abstract data types, including classes, polytypism etc. The quest for richer abstractions that allow less duplication in complex ...
Example: abstraction of integer sets (red) to sign sets (green) Let be an ordered set, called concrete set, and let ′ be another ordered set, called abstract set. These two sets are related to each other by defining total functions that map elements from one to the other.