Data Structure
Data structure is a particular way of organizing data in a computer so that it can be used efficiently.
Different kinds of data structures are suited to different kinds of
applications, and some are highly specialized to specific tasks. For
example, B-trees are particularly well-suited for implementation of databases, while compiler implementations usually use hash tables to look up identifiers.
Data structures provide a means to manage large amounts of data efficiently, such as large databases and internet indexing services. Usually, efficient data structures are a key in designing efficient algorithms. Some formal design methods and programming languages
emphasize data structures, rather than algorithms, as the key
organizing factor in software design. Storing and retrieving can be
carried out on data stored in both main memory and in secondary memory.
TYPES of Data structures:
- An array is a number of elements in a specific order. They are accessed using an integer to specify which element is required (although the elements may be of almost any type). Typical implementations allocate contiguous memory words for the elements of arrays (but this is not always a necessity). Arrays may be fixed-length or expandable.
- Records (also called tuples or structs) are among the simplest data structures. A record is a value that contains other values, typically in fixed number and sequence and typically indexed by names. The elements of records are usually called fields or members.
- An associative array (also called a dictionary or map) is a more flexible variation on a record, in which name-value pairs can be added and deleted freely. A hash table is a common implementation of an associative array.
- A union type specifies which of a number of permitted primitive types may be stored in its instances, e.g. "float or long integer". Contrast with a record, which could be defined to contain a float and an integer; whereas, in a union, there is only one value at a time. Enough space is allocated to contain the widest member datatype.
- A tagged union (also called a variant, variant record, discriminated union, or disjoint union) contains an additional field indicating its current type, for enhanced type safety.
- A set is an abstract data structure that can store specific values, without any particular order, and with no repeated values. Values themselves are not retrieved from sets, rather one tests a value for membership to obtain a boolean "in" or "not in".
- Graphs and trees are linked abstract data structures composed of nodes. Each node contains a value and also one or more pointers to other nodes. Graphs can be used to represent networks, while variants of trees can be used for sorting and searching, having their nodes arranged in some relative order based on their values.
- An object contains data fields, like a record, as well as various methods. In the context of object-oriented programming, records are known as plain old data structures to distinguish them from objects.
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