Hex editor

A hex editor (or binary file editor or byte editor) is a type of computer program that allows for manipulation of the fundamental binary data that constitutes a computer file. The name 'hex' comes from 'hexadecimal': a standard numerical format for representing binary data. A typical computer file occupies multiple areas on the platter(s) of a disk drive, whose contents are combined to form the file. Hex editors that are designed to parse and edit sector data from the physical segments of floppy or hard disks are sometimes called sector editors or disk editors.

With a hex editor, a user can see or edit the raw and exact contents of a file, as opposed to the interpretation of the same content that other, higher level application software may associate with the file format. For example, this could be raw image data, in contrast to the way image editing software would interpret and show the same file.

Hex editors may be used to correct data corrupted by system or application program problems where it may not be worthwhile to write a special program to make the corrections. They are useful to bypass application edit checks which may prevent correction of erroneous data. They have been used to "patch" executable programs to change or add a few instructions as an alternative to recompilation. Program fixes for IBM mainframe systems are sometimes distributed as patches rather than distributing a complete copy of the affected program.

In most hex editor applications, the data of the computer file is represented as hexadecimal values grouped in 4 groups of 4 bytes (or two groups of 8 bytes), followed by one group of 16 printable ASCII characters which correspond to each pair of hex values (each byte). Non-printable ASCII characters (e.g., Bell) and characters that would take more than one character space (e.g., tab) are typically represented by a dot (".") in the following ASCII field.

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