Data (computing)
Encyclopedia
In computer science
, data (icon or ˈ) is information in a form suitable for use with a computer
. Data is often distinguished from program
s. A program is a sequence of instructions that detail a task for the computer to perform. In this sense, data is thus everything that is not program code.
In an alternate usage, binary file
s (which are not human-readable
) are sometimes called "data" as distinguished from human-readable "text
". The total amount of digital data in 2007 was estimated to be 281 billion gigabytes (= 281 exabytes).
". In the nominal case, the program, as executed
by the computer, will consist of binary
machine code
. The elements of storage
manipulated by the program, but not actually executed by the CPU
, contain data.
Typically, different file
s are used to store programs vs data. Executable file
s contain programs; all other files are data file
s. However, executable files may also contain data which is "built-in" to the program. In particular, some executable files have a data segment
, which nominally contains constants and initial values (both data).
For example: a user
might first instruct the operating system
to load a word processor
program from one file, and then edit a document
stored in another file. In this example, the document would be considered data. If the word processor also features a spell checker
, then the dictionary (word list) for the spell checker would also be considered data. The algorithm
s used by the spell checker to suggest corrections would be considered code.
The line between program and data can become blurry. An interpreter
, for example, is a program. The input data to an interpreter is itself a program—just not one expressed in native machine language. In many cases, the interpreted program will be a human-readable text file
, which is manipulated with a text editor
—more normally associated with plain text
data. Metaprogramming
similarly involves programs manipulating other programs as data. Also, for programs like compilers, linkers, debuggers, program updaters, etc. may other programs serve as data. The most special case is the case of self-modifying code
, which manipulates itself.
Computer science
Computer science or computing science is the study of the theoretical foundations of information and computation and of practical techniques for their implementation and application in computer systems...
, data (icon or ˈ) is information in a form suitable for use with a computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
. Data is often distinguished from program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
s. A program is a sequence of instructions that detail a task for the computer to perform. In this sense, data is thus everything that is not program code.
In an alternate usage, binary file
Binary file
A binary file is a computer file which may contain any type of data, encoded in binary form for computer storage and processing purposes; for example, computer document files containing formatted text...
s (which are not human-readable
Human-readable
A human-readable medium or human-readable format is a representation of data or information that can be naturally read by humans.In computing, human-readable data is often encoded as ASCII or Unicode text, rather than presented in a binary representation...
) are sometimes called "data" as distinguished from human-readable "text
Text file
A text file is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists within a computer file system...
". The total amount of digital data in 2007 was estimated to be 281 billion gigabytes (= 281 exabytes).
Data vs programs
Fundamentally, computers follow the instructions they are given. A set of instructions to perform a given task (or tasks) is called a "programComputer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...
". In the nominal case, the program, as executed
Execution (computers)
Execution in computer and software engineering is the process by which a computer or a virtual machine carries out the instructions of a computer program. The instructions in the program trigger sequences of simple actions on the executing machine...
by the computer, will consist of binary
Binary file
A binary file is a computer file which may contain any type of data, encoded in binary form for computer storage and processing purposes; for example, computer document files containing formatted text...
machine code
Machine code
Machine code or machine language is a system of impartible instructions executed directly by a computer's central processing unit. Each instruction performs a very specific task, typically either an operation on a unit of data Machine code or machine language is a system of impartible instructions...
. The elements of storage
Computer storage
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
manipulated by the program, but not actually executed by the CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
, contain data.
Typically, different file
Computer file
A computer file is a block of arbitrary information, or resource for storing information, which is available to a computer program and is usually based on some kind of durable storage. A file is durable in the sense that it remains available for programs to use after the current program has finished...
s are used to store programs vs data. Executable file
Executable
In computing, an executable file causes a computer "to perform indicated tasks according to encoded instructions," as opposed to a data file that must be parsed by a program to be meaningful. These instructions are traditionally machine code instructions for a physical CPU...
s contain programs; all other files are data file
Data file
A data file is a computer file which stores data to use by a computer application or system. It generally does not refer to files that contain instructions or code to be executed , or to files which define the operation or structure of an application or system ; but specifically to information...
s. However, executable files may also contain data which is "built-in" to the program. In particular, some executable files have a data segment
Data segment
A data segment is a portion of virtual address space of a program, which contains the global variables and static variables that are initialized by the programmer...
, which nominally contains constants and initial values (both data).
For example: a user
User (computing)
A user is an agent, either a human agent or software agent, who uses a computer or network service. A user often has a user account and is identified by a username , screen name , nickname , or handle, which is derived from the identical Citizen's Band radio term.Users are...
might first instruct the operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
to load a word processor
Word processor
A word processor is a computer application used for the production of any sort of printable material....
program from one file, and then edit a document
Document file format
A document file format is a text or binary file format for storing documents on a storage media, especially for use by computers.There currently exist a multitude of incompatible document file formats....
stored in another file. In this example, the document would be considered data. If the word processor also features a spell checker
Spell checker
In computing, a spell checker is an application program that flags words in a document that may not be spelled correctly. Spell checkers may be stand-alone capable of operating on a block of text, or as part of a larger application, such as a word processor, email client, electronic dictionary,...
, then the dictionary (word list) for the spell checker would also be considered data. The algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
s used by the spell checker to suggest corrections would be considered code.
The line between program and data can become blurry. An interpreter
Interpreter (computing)
In computer science, an interpreter normally means a computer program that executes, i.e. performs, instructions written in a programming language...
, for example, is a program. The input data to an interpreter is itself a program—just not one expressed in native machine language. In many cases, the interpreted program will be a human-readable text file
Text file
A text file is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists within a computer file system...
, which is manipulated with a text editor
Text editor
A text editor is a type of program used for editing plain text files.Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code....
—more normally associated with plain text
Plain text
In computing, plain text is the contents of an ordinary sequential file readable as textual material without much processing, usually opposed to formatted text....
data. Metaprogramming
Metaprogramming
Metaprogramming is the writing of computer programs that write or manipulate other programs as their data, or that do part of the work at compile time that would otherwise be done at runtime...
similarly involves programs manipulating other programs as data. Also, for programs like compilers, linkers, debuggers, program updaters, etc. may other programs serve as data. The most special case is the case of self-modifying code
Self-modifying code
In computer science, self-modifying code is code that alters its own instructions while it is executing - usually to reduce the instruction path length and improve performance or simply to reduce otherwise repetitively similar code, thus simplifying maintenance...
, which manipulates itself.