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In programming languages a data type defines a set of values and the allowable operations on those values^[1]. For example, in the Java programming language, the "int" type represents the set of 32-bit integers ranging in value from -2,147,483,648 to 2,147,483,647, and the operations such as addition, subtraction, and multiplication that can be performed on integers. Almost all programming languages explicitly include the notion of data type, though different languages may use different terminology. Common data types in programming languages include those that represent integers, floating point numbers, and characters, and a language may support many more. Most programming languages also allow the programmer to define additional data types, usually by combining multiple elements of other types and defining the valid operations of the new data type. For example, a programmer might create a new data type named "Person" that specifies that data interpreted as Person would include a name and a date of birth.

A data type can also be thought of as a constraint placed upon the interpretation of data in a type system, describing representation, interpretation and structure of values or objects stored in computer memory. The type system uses data type information to check correctness of computer programs that access or manipulate the data.

Contents 1 Machine data types 2 Primitive types 3 Composite types 4 Abstract data types 5 Pointer and reference types 6 Algebraic types 7 Object types 8 Function types 9 See also 10 Notes 11 References

All data in computers based on digital electronics is represented as bits (alternatives 0 and 1) on the lowest level. The smallest addressable unit of data is a group of bits called a byte (usually an octet, which is 8 bits). The unit processed by machine code instructions is called a word (as of 2006, typically 32 or 64 bits). Most instructions interpret the word as a binary number, such that a 32-bit word can represent unsigned integer values from 0 to 2³² − 1 or signed integer values from − 2³¹ to 2³¹ − 1. Because of two's complement, the machine language and machine don't need to distinguish between these unsigned and signed data types for the most part.

There is a specific set of arithmetic instructions that use a different interpretation of the bits in word as a floating-point number.

Main article: Primitive type

Main article: Composite type

Further information: Tuple

Further information: Array

Further information: Storage record

Further information: Object composition

Main article: Abstract data type

Main article: Reference (computer science)

Further information: Pointer

Main article: Algebraic data type

Main article: Object (computer science)

Further information: Class (computer science)

Main article: Function type

• Type theory for the mathematical models of types
• Type system for different choices in programming language typing

1. ^ http://www.sigcse.org/cc2001/PL.html

• Luca Cardelli, Peter Wegner. On Understanding Types, Data Abstraction, and Polymorphism, [1] from Computing Surveys, (December, 1985)