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Uuencoding
uuencoding is a form of binary-to-text encoding that originated in the Unix programs uuencode and uudecode written by Mary Ann Horton at the University of California, Berkeley in 1980, for encoding binary data for transmission in email systems. The name "uuencoding" is derived from Unix-to-Unix Copy, i.e. "Unix-to-Unix encoding" is a safe encoding for the transfer of arbitrary files from one Unix system to another Unix system but without guarantee that the intervening links would all be Unix systems. Since an email message might be forwarded through or to computers with different character sets or through transports which are not 8-bit clean, or handled by programs that are not 8-bit clean, forwarding a binary file via email might cause it to be corrupted. By encoding such data into a character subset common to most character sets, the encoded form of such data files was unlikely to be "translated" or corrupted, and would thus arrive intact and unchanged at the destination. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binary-to-text Encoding
A binary-to-text encoding is code, encoding of data (computing), data in plain text. More precisely, it is an encoding of binary data in a sequence of character (computing), printable characters. These encodings are necessary for transmission of data when the communication channel does not allow binary data (such as email or NNTP) or is not 8-bit clean. Pretty Good Privacy, PGP documentation () uses the term "ASCII armor" for binary-to-text encoding when referring to Base64. Overview The basic need for a binary-to-text encoding comes from a need to communicate arbitrary binary data over preexisting communications protocols that were designed to carry only English language human-readable text. Those communication protocols may only be 7-bit safe (and within that avoid certain ASCII control codes), and may require line break (computing), line breaks at certain maximum intervals, and may not maintain whitespace (computer science), whitespace. Thus, only the 94 ASCII#ASCII printable c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radix-64
In computer programming, Base64 is a group of binary-to-text encoding schemes that transforms binary data into a sequence of printable characters, limited to a set of 64 unique characters. More specifically, the source binary data is taken 6 bits at a time, then this group of 6 bits is mapped to one of 64 unique characters. As with all binary-to-text encoding schemes, Base64 is designed to carry data stored in binary formats across channels that only reliably support text content. Base64 is particularly prevalent on the World Wide Web where one of its uses is the ability to embed image files or other binary assets inside textual assets such as HTML and CSS files. Base64 is also widely used for sending e-mail attachments, because SMTP – in its original form – was designed to transport 7-bit ASCII characters only. Encoding an attachment as Base64 before sending, and then decoding when received, assures older SMTP servers will not interfere with the attachment. Base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Percent-encoding
URL encoding, officially known as percent-encoding, is a method to binary-to-text encoding, encode arbitrary data in a uniform resource identifier (URI) using only the ASCII, US-ASCII characters legal within a URI. Although it is known as ''URL encoding'', it is also used more generally within the main Uniform Resource Identifier (URI) set, which includes both Uniform Resource Locator (URL) and Uniform Resource Name (URN). Consequently, it is also used in the preparation of data of the application/x-www-form-urlencoded media type, as is often used in the submission of HTML form (web), form data in HTTP requests. Percent-encoding is not Case sensitivity, case-sensitive. Types Percent-encoding in a URI Types of URI characters The characters allowed in a URI are either ''reserved'' or ''unreserved'' (or a percent sign, percent character as part of a percent-encoding). ''Reserved'' characters are those characters that sometimes have special meaning. For example, forward slash ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HFS Plus
HFS Plus or HFS+ (also known as Mac OS Extended or HFS Extended) is a journaling file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS 8.1. HFS+ continued as the primary Mac OS X file system until it was itself replaced with the Apple File System (APFS), released with macOS High Sierra in 2017. HFS+ is also one of the formats supported by the iPod digital music player. Compared to its predecessor HFS, also called ''Mac OS Standard'' or ''HFS Standard,'' HFS Plus supports much larger files (block addresses are 32-bit length instead of 16-bit) and using Unicode (instead of Mac OS Roman or any of several other character sets) for naming items. Like HFS, HFS Plus uses B-trees to store most volume metadata, but unlike most file systems that support hard links, HFS Plus supports hard links to directories. HFS Plus permits filenames up to 255 characters in length, and n-forke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Fork
A resource fork is a fork of a file on Apple's classic Mac OS operating system that is used to store structured data. It is one of the two forks of a file, along with the data fork, which stores data that the operating system treats as unstructured. Resource fork capability has been carried over to the modern macOS for compatibility. A resource fork stores information in a specific form, containing details such as icon bitmaps, the shapes of windows, definitions of menus and their contents, and application code ( machine code). For example, a word processing file might store its text in the data fork, while storing any embedded images in the same file's resource fork. The resource fork is used mostly by executables, but any file can have a resource fork. In a 1986 technical note, Apple strongly recommended that developers do not put general data into the resource fork of a file. According to Apple, there are parts of the system software that rely on resource forks having only v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hierarchical File System (Apple)
Hierarchical File System (HFS) is a proprietary file system developed by Apple Inc. for use in computer systems running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs. HFS is also referred to as Mac OS Standard (or HFS Standard), while its successor, HFS Plus, is also called Mac OS Extended (or HFS Extended). With the introduction of Mac OS X 10.6, Apple dropped support for formatting or writing HFS disks and images, which remained supported as read-only volumes until macOS 10.15. Starting with macOS 10.15, HFS disks can no longer be read. History Apple introduced HFS in September 1985, specifically to support Apple's first hard disk drive for the Macintosh, replacing the Macintosh File System (MFS), the original file system which had been introduced over a year and a half earlier with the first Macintosh computer. HFS drew heavily upon Apple's first operating system with a hierarchical file syste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fork (filesystem)
In a computer file system, a fork is a set of data associated with a file-system object. File systems without forks only allow a single set of data for the contents, while file systems with forks allow multiple such contents. Every non-empty file must have at least one fork, often of default type, and depending on the file system, a file may have one or more other associated forks, which in turn may contain primary data integral to the file, or just metadata. Unlike '' extended attributes'', a similar file system feature which is typically of fixed size, forks can be of variable size, possibly even larger than the file's primary data fork. The size of a file is the sum of the sizes of each fork. Popular file systems that can use forks include Apple's HFS+ and Microsoft's NTFS. Alternatives On file systems without forks, one may instead use multiple separate files that are associated with each other, particularly sidecar files for metadata. However, the connection between these f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line Feed
A newline (frequently called line ending, end of line (EOL), next line (NEL) or line break) is a control character or sequence of control characters in character encoding specifications such as ASCII, EBCDIC, Unicode, etc. This character, or a sequence of characters, is used to signify the end of a line (text file), line of text and the start of a new one. History In the mid-1800s, long before the advent of teleprinters and teletype machines, Morse code operators or telegraphists invented and used Prosigns for Morse code, Morse code prosigns to encode white space text formatting in formal written text messages. In particular, the International Morse code, Morse prosign (mnemonic break text), represented by the concatenation of literal textual Morse codes "B" and "T" characters, sent without the normal inter-character spacing, is used in Morse code to encode and indicate a ''new line'' or ''new section'' in a formal text message. Later, in the age of modern teleprinters, st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carriage Return
A carriage return, sometimes known as a cartridge return and often shortened to CR, or return, is a control character or mechanism used to reset a device's position to the beginning of a line of text. It is closely associated with the line feed and newline concepts, although it can be considered separately in its own right. Typewriters Originally, the term "carriage return" referred to a mechanism or lever on a typewriter. For machines where the type element was fixed and the paper held in a moving ''carriage'', this lever was on the left attached to the moving carriage, and operated after typing a line of text to cause the carriage to return to the far right so the type element would be aligned to the left side of the paper. The lever would also usually ''feed'' the paper to advance to the next line. Many electric typewriters such as IBM Electric or Underwood Electric made carriage return to be another key on the keyboard instead of a lever. The key was usually labeled "car ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Modulo
In computing and mathematics, the modulo operation returns the remainder or signed remainder of a division, after one number is divided by another, the latter being called the '' modulus'' of the operation. Given two positive numbers and , modulo (often abbreviated as ) is the remainder of the Euclidean division of by , where is the dividend and is the divisor. For example, the expression "5 mod 2" evaluates to 1, because 5 divided by 2 has a quotient of 2 and a remainder of 1, while "9 mod 3" would evaluate to 0, because 9 divided by 3 has a quotient of 3 and a remainder of 0. Although typically performed with and both being integers, many computing systems now allow other types of numeric operands. The range of values for an integer modulo operation of is 0 to . mod 1 is always 0. When exactly one of or is negative, the basic definition breaks down, and programming languages differ in how these values are defined. Variants of the definition In mathematics, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grave Accent
The grave accent () ( or ) is a diacritical mark used to varying degrees in French, Dutch, Portuguese, Italian, Catalan and many other Western European languages as well as for a few unusual uses in English. It is also used in other languages using the Latin alphabet, such as Mohawk and Yoruba, and with non-Latin writing systems such as the Greek and Cyrillic alphabets and the Bopomofo or Zhuyin Fuhao semi-syllabary. It has no single meaning, but can indicate pitch, stress, or other features. For the most commonly encountered uses of the accent in the Latin and Greek alphabets, precomposed characters are available. For less-used and compound diacritics, a combining character facility is available. A free-standing version of the symbol (), commonly called a backtick, also exists and has acquired other uses. Uses Pitch The grave accent first appeared in the polytonic orthography of Ancient Greek to mark a lower pitch than the high pitch of the acute accent. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
