C data types

In the C programming language, data types are declarations for memory locations or variables that determine the characteristics of the data that may be stored and the methods (operations) of processing that are permitted involving them.

The C language provides basic arithmetic types, such as integer and real number types, and syntax to build array and compound types. Several header files in the C standard library contain definitions of support types, that have additional properties, such as providing storage with an exact size, independent of the implementation.

Basic types

The C language provides the four basic arithmetic type specifiers char, int, float and double, and the modifiers signed, unsigned, short and long. The following table lists the permissible combinations to specify a large set of storage size-specific declarations.

The actual size of integer types varies by implementation. The standard only requires size relations between the data types and minimum sizes for each data type:

Double-precision floating-point format

Double-precision floating-point format is a computer number format that occupies 8 bytes (64 bits) in computer memory and represents a wide, dynamic range of values by using a floating point.

Double-precision floating-point format usually refers to binary64, as specified by the IEEE 754 standard, not to the 64-bit decimal format decimal64.

IEEE 754 double-precision binary floating-point format: binary64

Double-precision binary floating-point is a commonly used format on PCs, due to its wider range over single-precision floating point, in spite of its performance and bandwidth cost. As with single-precision floating-point format, it lacks precision on integer numbers when compared with an integer format of the same size. It is commonly known simply as double. The IEEE 754 standard specifies a binary64 as having:

This gives 15–17 significant decimal digits precision. If a decimal string with at most 15 significant digits is converted to IEEE 754 double precision representation and then converted back to a string with the same number of significant digits, then the final string should match the original. If an IEEE 754 double precision is converted to a decimal string with at least 17 significant digits and then converted back to double, then the final number must match the original.

Double (volleyball)

A double occurs in volleyball when a player, during a match, is credited with scoring at least ten times in one (or more) of five statistical categories: Aces, Kills, Blocks, Digs, and Assists. The term was apparently derived from similar basketball jargon; the expression "triple-double" was coined by former Los Angeles Lakers public relations director Bruce Jolesch in order to showcase Magic Johnson's versatility.

There are four main types of doubles:

Of the five statistical categories, double digit match totals are most common for assists, but rare for any positions other than setter. The next most frequent double-digit category is digs, which is most often attained by liberos or defensive specialists, but can be achieved by any strong defensive player. Kills are the third most common double-digit achievement category, occurring predominantly among hitters, especially outside hitters and middle blockers. Likewise, double-digit blocking numbers are preponderantly accomplished by middle blockers or outside hitters, but are much less common than double-digit kills. Rarest by far are double-digit aces, which even the most exceptional server is unlikely to attain once in a career.

Helix

A helix (pl: helixes or helices) is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helices are coil springs and the handrails of spiral staircases. A "filled-in" helix – for example, a spiral ramp – is called a helicoid. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices. The word helix comes from the Greek word ἕλιξ, "twisted, curved".

Types

Helices can be either right-handed or left-handed. With the line of sight along the helix's axis, if a clockwise screwing motion moves the helix away from the observer, then it is called a right-handed helix; if towards the observer, then it is a left-handed helix. Handedness (or chirality) is a property of the helix, not of the perspective: a right-handed helix cannot be turned to look like a left-handed one unless it is viewed in a mirror, and vice versa.

Phelix

Phelix is a high-speed stream cipher with a built-in single-pass message authentication code (MAC) functionality, submitted in 2004 to the eSTREAM contest by Doug Whiting, Bruce Schneier, Stefan Lucks, and Frédéric Muller. The cipher uses only the operations of addition modulo 2³², exclusive or, and rotation by a fixed number of bits. Phelix uses a 256-bit key and a 128-bit nonce, claiming a design strength of 128 bits. Concerns have been raised over the ability to recover the secret key if the cipher is used incorrectly.

Performance

Phelix is optimised for 32-bit platforms. The authors state that it can achieve up to eight cycles per byte on modern x86-based processors.

FPGA Hardware performance figures published in the paper "Review of stream cipher candidates from a low resource hardware perspective" are as follows:

Helix

Phelix is a slightly modified form of an earlier cipher, Helix, published in 2003 by Niels Ferguson, Doug Whiting, Bruce Schneier, John Kelsey, Stefan Lucks, and Tadayoshi Kohno; Phelix adds 128 bits to the internal state.

Helix (TV series)

Helix is an American science fiction thriller drama television series that aired on Syfy from January 10, 2014 to April 10, 2015. The series followed a team of scientists from the Centers for Disease Control and Prevention who travelled to a research facility in the Arctic to investigate a potential outbreak of disease. While there, they find themselves stuck in a life-or-death situation that could decide the future of humankind. The executive producers of Helix were Ronald D. Moore, Lynda Obst, Steven Maeda, and Cameron Porsandeh, with Maeda serving as day-to-day showrunner.

On April 29, 2015, Syfy announced that the show was canceled after two seasons.

Plot

Season 1

Researchers from the CDC, led by Dr. Alan Farragut, investigate a viral outbreak at an arctic bioresearch station, only to discover that it has disastrous and wider implications for the entire world. Proscribed genetic engineering research is being done by the Ilaria Corporation, the company running the research station, which seems more interested in containing knowledge of their activities than in resolving the outbreak. Attempts at quarantine result in mutiny and attempted escape, and communication with the outside is mysteriously cut off. It is unclear at first whether the goal is a bioweapon or to transform humans in some way, and there are two variants of the virus. The first, Narvik-A, is fatal with no cure. Those infected with the second virus, Narvik-B, become dangerously violent zombie-like "Vectors", spreading the infection to others, with a small percentage eventually regaining some normality if treated, as it seems several characters have already been infected and cured. Those cured seem to have the ability to control the infected. The "outbreak" is revealed to have been a cover story to recruit Julia Walker as an unwitting test subject by deceiving the CDC personnel into creating an anti-viral "cure", to benefit the Ilaria Corporation's objectives.