Jiffy (time)
Encyclopedia
Jiffy is an informal term for any unspecified short period of time
, as in "I'll be back in a jiffy". From this it has acquired a number of more precise applications for short, very short, or extremely short periods of time. Known since the 18th century, the word's origin is unclear, though one suggestion is that it was thieves' cant
for lightning.
to travel one centimeter (approximately 33.3564 picosecond
s).
It has since been redefined for different measurements depending on the field of study.
, a jiffy is the time between alternating current power cycles, 1/60 or 1/50 of a second in most building power supplies — see alternating current
.
, a jiffy is the duration of one tick of the system timer interrupt
. It is not an absolute time interval unit, since its duration depends on the clock interrupt frequency of the particular hardware platform.
Early microcomputer systems such as the Commodore 64
and many game consoles (which use television
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
systems, or 50.0 Hz with most PAL
systems. Within the Linux
operating system kernel, since release 2.6.13, on the Intel i386 platform a jiffy is by default 4 ms, or 1/250 of a second. The jiffy values for other Linux versions and platforms have typically varied between about 1 ms and 10 ms.
in a vacuum provides a convenient universal relationship between distance and time, so in physics
(particularly in quantum physics) and often in chemistry
, a jiffy is defined as the time taken for light to travel some specified distance. In astrophysics and quantum physics a jiffy is, as defined by Edward R. Harrison, the time it takes for light to travel one fermi, which is the size of a nucleon. One fermi is 10−15 m, so a jiffy is about 3 × 10−24 seconds.
One isolated author has used the word jiffy to denote the Planck time
of about 5.4 × 10−44 second
s, which is the time it would take light to travel a Planck length if ordinary geometry was still relevant at that scale. Scattered reports have presented that obscure proposal as an established fact. Ironically, some of those reports seem to be based on a poorly written previous version of this very Wikipedia-article.
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
, as in "I'll be back in a jiffy". From this it has acquired a number of more precise applications for short, very short, or extremely short periods of time. Known since the 18th century, the word's origin is unclear, though one suggestion is that it was thieves' cant
Thieves' cant
Thieves' cant or Rogues' cant was a secret language which was formerly used by thieves, beggars and hustlers of various kinds in Great Britain and to a lesser extent in other English-speaking countries...
for lightning.
Beginnings in measurement
The earliest technical usage for jiffy was defined by Gilbert Newton Lewis (1875–1946). He proposed a unit of time called the "jiffy" which was equal to the time it takes lightLight
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
to travel one centimeter (approximately 33.3564 picosecond
Picosecond
A picosecond is 10−12 of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to 31,700 years....
s).
It has since been redefined for different measurements depending on the field of study.
Use in electronics
In electronicsElectronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
, a jiffy is the time between alternating current power cycles, 1/60 or 1/50 of a second in most building power supplies — see alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
.
Use in computing
In computingComputing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, a jiffy is the duration of one tick of the system timer interrupt
Interrupt
In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution....
. It is not an absolute time interval unit, since its duration depends on the clock interrupt frequency of the particular hardware platform.
Early microcomputer systems such as the Commodore 64
Commodore 64
The Commodore 64 is an 8-bit home computer introduced by Commodore International in January 1982.Volume production started in the spring of 1982, with machines being released on to the market in August at a price of US$595...
and many game consoles (which use television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
s as a display device) commonly synchronize the system interrupt timer with the vertical frequency of the local television standard, either 59.94 Hz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
with NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
systems, or 50.0 Hz with most PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
systems. Within the Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
operating system kernel, since release 2.6.13, on the Intel i386 platform a jiffy is by default 4 ms, or 1/250 of a second. The jiffy values for other Linux versions and platforms have typically varied between about 1 ms and 10 ms.
Use in physics
The speed of lightSpeed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
in a vacuum provides a convenient universal relationship between distance and time, so in physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
(particularly in quantum physics) and often in chemistry
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
, a jiffy is defined as the time taken for light to travel some specified distance. In astrophysics and quantum physics a jiffy is, as defined by Edward R. Harrison, the time it takes for light to travel one fermi, which is the size of a nucleon. One fermi is 10−15 m, so a jiffy is about 3 × 10−24 seconds.
One isolated author has used the word jiffy to denote the Planck time
Planck time
In physics, the Planck time, , is the unit of time in the system of natural units known as Planck units. It is the time required for light to travel, in a vacuum, a distance of 1 Planck length...
of about 5.4 × 10−44 second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
s, which is the time it would take light to travel a Planck length if ordinary geometry was still relevant at that scale. Scattered reports have presented that obscure proposal as an established fact. Ironically, some of those reports seem to be based on a poorly written previous version of this very Wikipedia-article.
External links
- FOLDOC
- The Jargon File