A binary file is a computer 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...

 which may contain any type of data, encoded in binary

Binary numeral system

The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...

 form for computer storage and processing purposes; for example, computer document files

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....

 containing formatted text

Formatted text

Formatted text, styled text or rich text, as opposed to plain text, has styling information beyond the minimum of semantic elements: colours, styles , sizes and special features .-Terminology:...

. Many binary file format

File format

A file format is a particular way that information is encoded for storage in a computer file.Since a disk drive, or indeed any computer storage, can store only bits, the computer must have some way of converting information to 0s and 1s and vice-versa. There are different kinds of formats for...

s contain parts that can be interpreted as text; binary files that contain only textual data—without, for example, any formatting information—are called 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....

 files. In many cases, plain text files are considered to be different from binary files because binary files are made up of more than just plain text.
When downloading, a completely functional program without any installer is also often called program binary, or binaries (as opposed to the source code

Source code

In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...

).

Structure

Unlike Text files, there is no special character present in the binary mode files to mark End-of-file

End-of-file

In computing, end of file is a condition in a computer operating system where no more data can be read from a data source...

. The binary mode files keep track of the end-of-file from number of characters present in the dictionary entry of the file.
Binary files are usually thought of as being a sequence of byte

Byte

The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...

s, which means the binary digits (bit

Bit

A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

s) are grouped in eights. Binary files typically contain bytes that are intended to be interpreted as something other than text character

Character (computing)

In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language....

s. Compiled computer programs are typical examples; indeed, compiled applications (object file

Object file

An object file is a file containing relocatable format machine code that is usually not directly executable. Object files are produced by an assembler, compiler, or other language translator, and used as input to the linker....

s) are sometimes referred to, particularly by programmers, as binaries. But binary files can also contain images, sounds, compressed versions of other files, etc. — in short, any type of file content whatsoever.

Some binary files contain headers

Header (information technology)

In information technology, header refers to supplemental data placed at the beginning of a block of data being stored or transmitted. In data transmission, the data following the header are sometimes called the payload or body....

, blocks of metadata

Metadata

The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

 used by a computer 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...

 to interpret the data in the file. For example, a GIF

GIF

The Graphics Interchange Format is a bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability....

 file can contain multiple images, and headers are used to identify and describe each block of image data. If a binary file does not contain any headers, it may be called a flat binary file. But the presence of headers are also common in plain text files, like email and html files.

Manipulation

To send binary files through certain systems (such as e-mail

E-mail

Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

) that do not allow all data values, they are often translated into a plain text representation (using, for example, Base64

Base64

Base64 is a group of similar encoding schemes that represent binary data in an ASCII string format by translating it into a radix-64 representation...

). Encoding the data has the disadvantage of increasing the file size during the transfer (for example, using Base64 will increase the file's size by approximately 30%), as well as requiring translation back into binary after receipt. The increased size may be countered by lower-level link compression, as the resulting text data will have about as much less entropy as it has increased size, so the actual data transferred in this scenario would likely be very close to the size of the original binary data. See Binary-to-text encoding for more on this subject.

Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 and its standard libraries allow the programmer to specify a parameter indicating if a file is expected to be plain text or binary when opening a file; this affects the standard library calls to read and write from the file in that the system converts between the "line break" character (the ASCII linefeed character) and the line break sequence the operating system expects applications to use in files (the linefeed and carriage return characters in sequence). Unix

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 also allows this, but there are no distinctions between text and binary files for the system to make, as Unix only uses a single line feed character to store a line break in files. This reflects the fact that the distinction between the two types of files is to a certain extent arbitrary

Arbitrary

Arbitrariness is a term given to choices and actions subject to individual will, judgment or preference, based solely upon an individual's opinion or discretion.Arbitrary decisions are not necessarily the same as random decisions...

.

Viewing

A hex editor

Hex editor

A hex editor is a type of computer program that allows a user to manipulate the fundamental binary data that makes up computer files. Note that computer files can be very small to very large...

 or viewer may be used to view file data as a sequence of hexadecimal (or decimal, binary or ASCII character) values for corresponding bytes of a binary file.

If a binary file is opened in 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....

, each group of eight bits will typically be translated as a single character, and you will see a (probably unintelligible) display of textual characters. If the file is opened in some other application, that application will have its own use for each byte: maybe the application will treat each byte as a number and output a stream of numbers between 0 and 255 — or maybe interpret the numbers in the bytes as colors and display the corresponding picture. If the file is itself treated as an executable

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...

 and run, then the operating system will attempt to interpret the file as a series of instructions in its machine language.

Interpretation

Standards are very important to binary files. For example, a binary file interpreted by the ASCII character set will result in text being displayed. A custom application can interpret the file differently, a byte may be a sound, or a pixel, or even an entire word. Binary itself is meaningless, until such time as an executed algorithm defines what should be done with each bit, byte, word or block. Thus, just examining the binary and attempting to match it against known formats can lead to the wrong conclusion as to what it actually represents. This fact can be used in steganography

Steganography

Steganography is the art and science of writing hidden messages in such a way that no one, apart from the sender and intended recipient, suspects the existence of the message, a form of security through obscurity...

, where an algorithm interprets a binary data file differently to reveal hidden content. Without the algorithm, it is impossible to tell that hidden content exists.

Binary compatibility

Two files that are binary compatible will have the same pattern of zeros and ones in the data portion of the file. The file header, however, may be different.

The term is used most commonly to state that data files produced by one application are exactly the same as data files produced by another application. For example, some software companies produce applications for Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 and the Macintosh

Macintosh

The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...

that are binary compatible, which means that a file produced in a Windows environment is interchangeable with a file produced on a Macintosh. This avoids many of the conversion problems caused by importing and exporting data.