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In engineering, some methods or components make special demands on the system. The extra design features necessary to meet these demands are called overhead. For instance, in electrical engineering, a particular integrated circuit might draw large current, requiring a robust power delivery circuit and a heat-dissipation mechanism.
An example from software engineering is the encoding of information and data. The date and time "2011-07-12 07:18:47" can be expressed as Unix time with the 32-bit signed integer 1310447927, consuming only 4 bytes. Represented as ISO 8601 formatted UTF-8 encoded string 2011-07-12 07:18:47 the date would consume 19 bytes, a size overhead of 375% over the binary integer representation. As XML this date can be written as follows with an overhead of 218 characters, while adding the semantic context that it is a CHANGEDATE with index 1.
<?xml version="1.0" encoding="UTF-8"?><DATETIMEqualifier="CHANGEDATE"index="1"><YEAR>2011</YEAR><MONTH>07</MONTH><DAY>12</DAY><HOUR>07</HOUR><MINUTE>18</MINUTE><SECOND>47</SECOND></DATETIME>The 349 bytes resulting from the UTF-8 encoded XML correspond to a size overhead of 8725% over the original integer representation.
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In computing and electronic systems, binary-coded decimal (BCD) is a class of binary encodings of decimal numbers where each digit is represented by a fixed number of bits, usually four or eight. Sometimes, special bit patterns are used for a sign or other indications.
Character encoding is the process of assigning numbers to graphical characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using computers. The numerical values that make up a character encoding are known as code points and collectively comprise a code space, a code page, or character map.
While Hypertext Markup Language (HTML) has been in use since 1991, HTML 4.0 from December 1997 was the first standardized version where international characters were given reasonably complete treatment. When an HTML document includes special characters outside the range of seven-bit ASCII, two goals are worth considering: the information's integrity, and universal browser display.
In computing, plain text is a loose term for data that represent only characters of readable material but not its graphical representation nor other objects. It may also include a limited number of "whitespace" characters that affect simple arrangement of text, such as spaces, line breaks, or tabulation characters. Plain text is different from formatted text, where style information is included; from structured text, where structural parts of the document such as paragraphs, sections, and the like are identified; and from binary files in which some portions must be interpreted as binary objects.
Unicode, formally The Unicode Standard, is a text encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 of the standard defines 154998 characters and 168 scripts used in various ordinary, literary, academic, and technical contexts.
Web pages authored using HyperText Markup Language (HTML) may contain multilingual text represented with the Unicode universal character set. Key to the relationship between Unicode and HTML is the relationship between the "document character set", which defines the set of characters that may be present in an HTML document and assigns numbers to them, and the "external character encoding", or "charset", used to encode a given document as a sequence of bytes.
UTF-8 is a character encoding standard used for electronic communication. Defined by the Unicode Standard, the name is derived from Unicode Transformation Format – 8-bit. Almost every webpage is stored in UTF-8.
The byte-order mark (BOM) is a particular usage of the special Unicode character code, U+FEFFZERO WIDTH NO-BREAK SPACE, whose appearance as a magic number at the start of a text stream can signal several things to a program reading the text:
UTF-32 (32-bit Unicode Transformation Format), sometimes called UCS-4, is a fixed-length encoding used to encode Unicode code points that uses exactly 32 bits (four bytes) per code point (but a number of leading bits must be zero as there are far fewer than 232 Unicode code points, needing actually only 21 bits). In contrast, all other Unicode transformation formats are variable-length encodings. Each 32-bit value in UTF-32 represents one Unicode code point and is exactly equal to that code point's numerical value.
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.
Unary coding, or the unary numeral system and also sometimes called thermometer code, is an entropy encoding that represents a natural number, n, with a code of length n + 1, usually n ones followed by a zero or with n − 1 ones followed by a zero. For example 5 is represented as 111110 or 11110. Some representations use n or n − 1 zeros followed by a one. The ones and zeros are interchangeable without loss of generality. Unary coding is both a prefix-free code and a self-synchronizing code.
In computer science, primitive data types are a set of basic data types from which all other data types are constructed. Specifically it often refers to the limited set of data representations in use by a particular processor, which all compiled programs must use. Most processors support a similar set of primitive data types, although the specific representations vary. More generally, primitive data types may refer to the standard data types built into a programming language. Data types which are not primitive are referred to as derived or composite.
A Java class file is a file containing Java bytecode that can be executed on the Java Virtual Machine (JVM). A Java class file is usually produced by a Java compiler from Java programming language source files containing Java classes. If a source file has more than one class, each class is compiled into a separate class file. Thus, it is called a .class file because it contains the bytecode for a single class.
This article compares Unicode encodings in two types of environments: 8-bit clean environments, and environments that forbid the use of byte values with the high bit set. Originally, such prohibitions allowed for links that used only seven data bits, but they remain in some standards and so some standard-conforming software must generate messages that comply with the restrictions. The Standard Compression Scheme for Unicode and the Binary Ordered Compression for Unicode are excluded from the comparison tables because it is difficult to simply quantify their size.
Overhead in computer systems consists of shared functions that benefit all users or processes but are not directly attributable to any specific task. It is thus similar to overhead in organizations. Computer system overhead shows up as slower processing, less memory, less network bandwidth, or bigger latency than would be expected from reading the system specifications. It is a special case of engineering overhead. Overhead can be a deciding factor in software design, with regard to structure, error correction, and feature inclusion. Examples of computing overhead may be found in Object Oriented Programming (OOP), functional programming, data transfer, and data structures.
A Canonical S-expression is a binary encoding form of a subset of general S-expression. It was designed for use in SPKI to retain the power of S-expressions and ensure canonical form for applications such as digital signatures while achieving the compactness of a binary form and maximizing the speed of parsing.
Action Message Format (AMF) is a binary format used to serialize object graphs such as ActionScript objects and XML, or send messages between an Adobe Flash client and a remote service, usually a Flash Media Server or third party alternatives. The Actionscript 3 language provides classes for encoding and decoding from the AMF format.
BSON is a computer data interchange format. The name "BSON" is based on the term JSON and stands for "Binary JSON". It is a binary form for representing simple or complex data structures including associative arrays, integer indexed arrays, and a suite of fundamental scalar types. BSON originated in 2009 at MongoDB. Several scalar data types are of specific interest to MongoDB and the format is used both as a data storage and network transfer format for the MongoDB database, but it can be used independently outside of MongoDB. Implementations are available in a variety of languages such as C, C++, C#, D, Delphi, Erlang, Go, Haskell, Java, JavaScript, Julia, Lua, OCaml, Perl, PHP, Python, Ruby, Rust, Scala, Smalltalk, and Swift.
LEB128 or Little Endian Base 128 is a variable-length code compression used to store arbitrarily large integers in a small number of bytes. LEB128 is used in the DWARF debug file format and the WebAssembly binary encoding for all integer literals.
Virtual Token Descriptor for eXtensible Markup Language (VTD-XML) refers to a collection of cross-platform XML processing technologies centered on a non-extractive XML, "document-centric" parsing technique called Virtual Token Descriptor (VTD). Depending on the perspective, VTD-XML can be viewed as one of the following: