Hexadecimal and also octal are common because these digits allow one to see which bits in a byte are set. Pairs of hexadecimal digits (each pair can represent a byte) are the current standard, because the vast majority of machines and file formats in use today handle data in units or groups of 8-bit bytes. A program called SUPERZAP (AMASPZAP) was available for IBM OS/360 systems which could edit raw disk records and also understood the format of executable files. In some special circumstances it was convenient to be able to access the data as a series of raw digits. Since the invention of computers and their different uses, a variety of file formats has been created. Unlike conventional text editors, Hex editors are able to efficiently handle files with indefinite sizes, as only a portion of the file is loaded while browsing it and modified when saving it, rather than the entire file at once. 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. 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). Program fixes for IBM mainframe systems are sometimes distributed as patches rather than distributing a complete copy of the affected program. They have been used to "patch" executable programs to change or add a few instructions as an alternative to recompilation. They are useful to bypass application edit checks which may prevent correction of erroneous data. 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. For example, this could be raw image data, in contrast to the way image editing software would interpret and show the same file. 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. Screenshot of a common hex editor (hexedit by Pascal Rigaux (Pixel))
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