EO, or Eight Ones, is an 8-bit
EBCDIC
Extended Binary Coded Decimal Interchange Code (EBCDIC; ) is an eight- bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems. It descended from the code used with punched cards and the corresponding si ...
character code
Character encoding is the process of assigning numbers to graphical character (computing), characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using computers. The numerical v ...
represented as all ones (
binary
Binary may refer to:
Science and technology Mathematics
* Binary number, a representation of numbers using only two values (0 and 1) for each digit
* Binary function, a function that takes two arguments
* Binary operation, a mathematical op ...
1111 1111,
hexadecimal
Hexadecimal (also known as base-16 or simply hex) is a Numeral system#Positional systems in detail, positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbo ...
FF).
As a control code
Eight Ones, as an
EBCDIC control code, is used for synchronisation purposes, such as a time and media filler.
In
Advanced Function Presentation
Advanced Function Presentation (AFP) is a presentation architecture and family of associated printer software and hardware that provides for document and information presentation independent of specific applications and devices.
Using AFP, users ...
code page definition resource headers, setting at least the first two bytes of the field for the eight-byte code page resource name (which is encoded in
code page 500
In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication cha ...
) to Eight Ones (0xFF) constitutes a "null name", which is treated as unset.
Mapping
When translated from the EBCDIC character set to
code page
In computing, a code page is a character encoding and as such it is a specific association of a set of printable character (computing), characters and control characters with unique numbers. Typically each number represents the binary value in a s ...
s with a
C1 control code set
The C0 and C1 control code or control character sets define control codes for use in text by computer systems that use ASCII and derivatives of ASCII. The codes represent additional information about the text, such as the position of a cursor, a ...
, Eight Ones is typically mapped to
hexadecimal
Hexadecimal (also known as base-16 or simply hex) is a Numeral system#Positional systems in detail, positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbo ...
code 0x9F, in order to provide a unique character mapping in both directions.
Prior to 1986, however, the C1 control code 0x9F was usually mapped to EBCDIC 0xE1, which was frequently used as a
numeric (figure) space in code pages at the time (including the
pre-1986 version of code page 37).
The
Unix utility follows the earlier convention, mapping the C1 code 0x9F to EBCDIC 0xE1, and mapping 0xFF (Eight Ones) to 0xFF.
As a graphical character
While Eight Ones is treated as a control code by IBM EBCDIC infrastructure, EBCDIC code pages from
Fujitsu Siemens
Fujitsu Siemens Computers GmbH was a Japanese and German vendor of information technology. The company was founded in 1999 as a 50/50 joint venture between Fujitsu of Japan and Siemens AG of Germany. On April 1, 2009, the company became Fujitsu ...
used on the
BS2000
BS2000 is an operating system for IBM 390-compatible mainframe computers developed in the 1970s by Siemens (Data Processing Department EDV) and from early 2000s onward by Fujitsu Technology Solutions.
Unlike other mainframe systems, BS2000 prov ...
system frequently use it for a graphical character, most often the
tilde
The tilde (, also ) is a grapheme or with a number of uses. The name of the character came into English from Spanish , which in turn came from the Latin , meaning 'title' or 'superscription'. Its primary use is as a diacritic (accent) in ...
. In these cases, the C1 control code 0x9F is mapped to a different location in the EBCDIC code page, most commonly 0x5F.
See also
*
0xFF
255 (two hundred ndfifty-five) is the natural number following 254 and preceding 256.
In mathematics
Its factorization makes it a sphenic number. Since 255 = 28 – 1, it is a Mersenne number (though not a pernicious one), and the fourth such n ...
*
Delete character
The delete control character (also called DEL or rubout) is the last character in the ASCII repertoire, with the code 127. It is supposed to do nothing and was designed to erase incorrect characters on paper tape. It is denoted as in caret notat ...
References
{{compsci-stub
Control characters