Jiffy can be an informal term for any unspecified short period, as in "I will be back in a jiffy". From this, it has acquired a number of more precise applications as the name of multiple

units of measurement A unit of measurement, or unit of measure, is a definite magnitude (mathematics), magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other qua ...

, each used to express or measure very brief durations of time. First attested in 1780, the word's origin is unclear, though one suggestion is that it was

thieves' cant Thieves' cant (also known as thieves' argot, rogues' cant, or peddler's French) is a cant (language), cant, cryptolect, or argot which was formerly used by thieves, beggars, and hustlers of various kinds in Great Britain and to a lesser extent i ...

for lightning. It was common in a number of Scots English dialects and in John Jamieson's ''Etymological Dictionary of the Scottish Language'' (1808) it is suggested that it is a corruption of ' gliff' (glimpse) or 'gliffin' (glance) (compare: 'in the blink of an eye') and may ultimately derive from Gothic or Teutonic words for 'shine'. ('Gliff' or 'gliss' for 'a transient view' was also found in older English poetry as early as 1738.)

Beginnings in measurement

The earliest technical usage for jiffy was defined by Gilbert Newton Lewis (1875–1946). He proposed in 1926 a

unit of time A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world, is the second, defined as ...

called the "jiffy" which was equal to the time it takes

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

to travel one centimeter in vacuum (approximately 33.3564 picoseconds). It has since been redefined for different measurements depending on the field of study.

Uses

Electronics

electronics Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other Electric charge, electrically charged particles. It is a subfield ...

, a jiffy is the period of an

alternating current Alternating current (AC) is an electric current that periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction. Alternating current is the form in w ...

power cycle, 1/60 or 1/50 of a second in most

mains power Mains electricity, utility power, grid power, domestic power, wall power, household current, or, in some parts of Canada, hydro, is a general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is de ...

supplies.

Computing

computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and softw ...

, a jiffy was originally the time between two ticks of the

system time In computer science and computer programming, system time represents a computer system's notion of the passage of time. In this sense, ''time'' also includes the passing of calendar date, days on the calendar. System time is measured by a ''sys ...

interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted ...

. It is not an absolute time interval unit, since its duration depends on the clock interrupt frequency of the particular hardware platform. Many older game consoles (which use

television Television (TV) is a telecommunication medium for transmitting moving images and sound. Additionally, the term can refer to a physical television set rather than the medium of transmission. Television is a mass medium for advertising, ...

s as a display device) commonly synchronize the system interrupt timer with the vertical frequency of the local television standard, either 59.94 Hz with

NTSC NTSC (from National Television System Committee) is the first American standard for analog television, published and adopted in 1941. In 1961, it was assigned the designation System M. It is also known as EIA standard 170. In 1953, a second ...

systems, or 50.0 Hz (20 ms) with most

PAL Phase Alternating Line (PAL) is a color encoding system for analog television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

systems. Some 1980s 8-bit Commodore computers, such as the

PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive/ cute appearances, inte ...

VIC-20 The VIC-20 (known as the VC-20 in Germany and the VIC-1001 in Japan) is an 8-bit entry level home computer that was sold by Commodore International, Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commod ...

/ C64, had a jiffy of 1/60 second, which was not dependent on the mains AC or video vertical refresh rate. A timer in the computer creates the 60 Hz rate, causing an interrupt service routine to be executed every 1/60 second, incrementing a 24-bit jiffy counter, scanning the keyboard, and handling some other housekeeping. Jiffy values for various

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

versions and platforms have typically varied between about 1 ms and 10 ms, with 10 ms (1/100 s) reported as an increasingly common standard in the

Jargon File The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT Computer Science and Artificial Intelligence Laboratory, MIT AI Lab ...

.Entry on ''jiffy''
in

The Jargon File The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT AI Lab, the Stanford AI Lab (SAIL) and others of the old ARPANE ...

Stratus VOS Stratus VOS (Virtual Operating System) is a proprietary operating system running on Stratus Technologies fault-tolerant computer systems. VOS is available on Stratus's ftServer and Continuum platforms. VOS customers use it to support high-volu ...

(Virtual Operating System) uses a jiffy of 1/65,536 second to express date and time (number of jiffies elapsed since . Stratus also defines the microjiffy, being 1/65,536 of a regular jiffy. The term ''jiffy'' is sometimes used in

computer animation Computer animation is the process used for digitally generating Film, moving images. The more general term computer-generated imagery (CGI) encompasses both still images and moving images, while computer animation refers to moving images. Virtu ...

as a method of defining playback rate, with the delay interval between individual frames specified in 1/100 of a second (10 ms) jiffies, particularly in Autodesk Animator .FLI sequences (one global frame frequency setting) and animated

Compuserve CompuServe, Inc. (CompuServe Information Service, Inc., also known by its initialism CIS or later CSi) was an American Internet company that provided the first major commercial online service provider, online service. It opened in 1969 as a times ...

.GIF images (each frame having an individually defined display time measured in 1/100 s).

Science

The

speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...

in vacuum provides a convenient universal relationship between distance and time, so in

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

(particularly in

quantum physics Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...

) and often in

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, a jiffy is defined as the time taken for light to travel some specified distance. In

astrophysics Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the ...

and quantum physics a jiffy is, as defined by Edward R. Harrison,"The Cosmic Numbers" in ''Cosmology, The Science of the Universe'', 1981 Cambridge Press the time it takes for light to travel one fermi, which is approximately the size of a

nucleon In physics and chemistry, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines the atom's mass number. Until the 1960s, nucleons were thought to be ele ...

. One fermi is , so a jiffy is about . It has also more informally been defined as "one light-foot", which is equal to approximately one

nanosecond A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or seconds. The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit (e ...

References

External links

* FOLDOC {{Time measurement and standards Jiffy Jiffy#Use in computing Jiffy#Use in computing