Gcal 3.01
N. Glossary
Here is an alphabetical list of most terms with short description
that are introduced and used in this manual:
- Actual date modifier
-
Gcal uses that date as today's date which is declared by the actual date
modifier, instead of using the date that is given by computer's clock
as system date.
- Alternation operator
-
The `|' metacharacter is used to specify alternatives
in a regular expression.
- Amateur-astronomical twilight
-
The time when the center of the Sun passes a reference
altitude of 15 degrees below a mathematical horizon.
- Anchor
-
The `^' and `$' metacharacters in a regular expression.
- ANSI
-
The American National Standards Institute. This organization produces many
standards, among them the standards for the C and C++ programming languages.
- Asr prayer time
-
The third Islamic prayer time. Begins in the afternoon when
the length of the shadow cast by a vertical pole has a definite length,
and ends just before sunset.
- Astronomical twilight
-
The time when the center of the Sun passes a reference
altitude of 18 degrees below a mathematical horizon.
- Astronomical unit
-
An astronomical unit, abbreviated by ae, is equal to the mean
distance of the Sun from the Earth, which is about 149,597,870.691
kilometers.
- Autumnal equinox point on the ecliptic
-
The point where the descending Sun's orbit intersects the celestial equator.
- Azimuth
-
The horizontal angular distance between the vertical circle,
that passes a celestial body, and the North point.
- Biorhythm
-
Ascending and descending curves which show three coherent biological
cycles, the physical, the emotional and the intellectual cycle.
- BSD
-
Short term for Berkeley Software Distribution,
a Unix operating system variant.
- C
-
The system programming language that most GNU software is written in.
- Calendar option class
-
The option which control the calendar layout.
- Celestial axis
-
The connecting line which runs between the celestial North and South Pole.
- Celestial body elevation
-
The vertical angular distance between the celestial body and the horizon.
- Celestial equator
-
A celestial great circle, which is vertical to the celestial axis
and simultaneously represents the Earth's equator that is projected
onto the celestial sphere.
- Celestial Pole
-
The northern and southern lengthening of the Earth's rotation axis,
respectively, projected on the celestial sphere.
- Character class
-
A character class in a regular expression is a special notation for
describing lists of characters that have a specific attribute, but
where the actual characters themselves can vary from country to
country and/or from character set to character set.
- Character list
-
Matches any one of the characters that are enclosed in the
square brackets in a text, which is processed by a regular expression.
- Character set
-
The set of numeric codes used by a computer system to represent the characters
(letters, numbers, punctuation, etc.) of a particular country or place. The
most common character set in use today is ASCII (American Standard
Code for Information Interchange). Many European countries use an extension
of ASCII known as ISO-8859-1
(ISO Latin-1).
- Civil Islamic calendar
-
The arithmetically determined Islamic lunar calendar.
- Civil midnight time
-
In terms of Gcal, this is 0 o'clock, the day change just took part.
This clocktime is alternatively also denoted as 24 o'clock, or 12pm.
- Civil twilight
-
The time when the center of the Sun passes a reference
altitude of 6 degrees below a mathematical horizon.
- Collating element
-
A special sequence that can appear in a character lists of a regular
expression. This apply to non-ASCII character sets, which can
have single symbols that are represented with more than one character,
as well as several characters that are equivalent for collating,
or sorting, purposes.
- Collating symbol
-
A multi-character collating element of a regular expression that
is enclosed in `[.' and `.]' metacharacters.
- Command line argument
-
A special text that is mostly given on the command line to run Gcal,
and which serves for controlling the program.
- Command
-
A special type of command line argument
which controls the periods Gcal respects.
- Common option class
-
The standard options all GNU software should implement at least partially.
- Conjunction
-
A celestial body is either behind the Sun or is between Sun and Earth
(seen from the Earth), and is therefore non-visible from the Earth.
In terms of the Moon, this is the New Moon phase.
- Critical day
-
Those days in the biorhythm in which one or more of the biological cycles
crosses the zero point. At that time, one's system is said to be in a state
of flux and it may be desirable to exhibit caution.
- Cycle mode
-
The dynamical, i.e. depending on the respective clocktime, Sun and Moon
oriented special texts are calculated for a series of clocktimes for the
current day, i.e. determination is done for any time interval that can
be individually defined by the user.
- Date part
-
That part of a Gcal resource file line that contains the information
at which date a fixed date happens.
- Decimal system
-
Base-ten notation, where the digits are
0...9.
- Declination
-
The vertical angular distance between the center of a celestial body
and the celestial equator.
- Delta-t
-
Delta-t is the difference between the Terrestrial Dynamical time
(abbreviated by TDT), that was formerly known as Ephemeris
time (abbreviated by ET), and the Universal time (UT).
Thus, `delta-t == TDT - UT'.
- Early years
-
In terms of eternal holidays that are determined by Gcal, these are the years
within the period AD 30 until the midth of the 20th century.
- Ecliptic latitude
-
The vertical angular distance between the center of a celestial body
and the ecliptic.
- Ecliptic longitude
-
The vertical angular distance between the center of a celestial body
and the vernal equinox point on the ecliptic.
- Ecliptic
-
The zodiacal line or Sun's orbit.
- Elongation
-
The horizontal angular distance between the center of a celestial body
and the Sun's center, as seen from the Earth.
- Ending date
-
A part of a Gcal special text that defines the last
or latest date at which the fixed date may occur.
- Environment
-
A collection of strings, of the form
name=value,
that each program has available to it. Users generally place values into
the environment in order to provide information to various programs.
Typical examples are the environment variables HOME and PATH.
- Equation of time
-
A correction to be added to the true solar time --as read on a sundial---
to obtain the mean solar time.
- Equivalence class
-
A list of equivalent characters of a regular expression
that is enclosed in `[=' and `=]' metacharacters.
- Escape sequence
-
A special sequence of characters used for describing non-printing characters,
such as
\E or \033 or \x1B for the ASCII
ESC (escape) character itself.
- Evening width
- Set width
-
The horizontal angular distance between the set azimuth of a celestial body
and the West direction.
- Exclusive day period
- Exclusive date period
-
A Gcal special text that can be specified with the effect,
that only those fixed dates are respected and displayed
which are not part of a definite period.
- Extended file name
-
A name that contains one ore more `/' characters, and which denotes
a file, whose fixed access path either starts from the root file directory,
like `/foo/bar/file', or from the actual file directory,
like `./bar/file' or `../bar/file'.
- Extended language code information
-
A simple language code information, which additionally has a
territory information that is separated by a `_', like
en_us for american English.
- Fajr prayer time
-
The first Islamic prayer time. Begins with the beginning of astronomical
morning twilight, and ends just before sunrise.
- Fixed date option class
-
The options which control the fixed date layout and intensity.
- Format instruction
-
Text variables, special texts and date formats can be provided with such
an instruction text that results the special representation of the contents
of text variables, and the evaluated special texts and date formats.
- FSF
- Free Software Foundation
-
A non-profit organization dedicated to the production and distribution
of freely distributable software. It was founded by Richard M. Stallman,
the author of the original Emacs editor.
- Geocentric data
-
Observations of celestial bodies that are done from the
fictitious center of the Earth yield in geocentrically based values.
- Geocentrical horizon
-
That fictitious horizontal plane that passes through the Earth's center,
orthogonal to the observer's local vertical.
- Geometrical horizon
- Mathematical horizon
- Mathematical-geocentric horizon
-
A purely geometrically-built horizon which disregards the phenomenon of
refraction as it arises in reality by the influence of the Earth's atmosphere.
- Global date variable
-
A Gcal date variable, which is defined in the command line.
Is visible in all referenced resource files.
- Global option class
-
The options which modify the program output.
- Global text variable
-
A Gcal text variable, which is defined in the command line.
Is visible in all referenced resource files.
- Gnomon
-
A vertical pole which is used to ascertain the length of a shadow.
- GNU
-
GNU's not Unix. An on-going project of the Free Software Foundation
to create a complete, freely distributable, POSIX-compliant computing
environment.
- GPL
- General Public License
-
The terms under which Gcal and its source code may be distributed.
- Gregorian calendar
-
The calendar which was introduced in AD 1582 by Pope Gregory XIII,
that has an average year length of 365.2425 days. This calendar is most
respected around the world today.
- Hexadecimal system
-
Base 16 notation, where the digits are
0...9 and
A...F, with `A' representing 10, `B'
representing 11, and so on up to `F' for 15.
- Highest culmination point
-
The highest point above or below the horizontal plane
which transits a celestial body during a day.
- Highlighting sequence
-
A control character sequence which cause a color or intensity switch in
output text. Typical control character sequences are the ANSI
escape sequences which have a leading escape character, and trailing more
characters that define the type of the ANSI escape sequence.
- Horizontal parallax
-
The horizontal parallax of a celestial body specifies the diameter
of the Earth as it is seen from the surface of the celestial body.
- Hybrid calendar mode
-
The automatical change from one calendar system to another if there
are relations to a date for which the other calendar system is valid.
Thus, Gcal automatically changes from the Julian calendar system to the
Gregorian calendar system if output is related to dates after the
Gregorian Reformation has happened.
- Inclusive day period
- Inclusive date period
-
A Gcal special text that can be specified with the effect,
that only those fixed dates are respected and displayed
which are part of a definite period.
- Integer number
-
A whole number, i.e. a number that does not have a fractional part.
- Interval expression
-
One or two numbers inside braces in a regular expression.
- Isha prayer time
-
The fifth Islamic prayer time. Begins at the end of the astronomical
evening twilight, and ends just before the astronomical midnight time
of the Sun.
- ISO
-
ISO is the abbreviation of International Organization
for Standardization.
- ISO week number
-
The week starts on a Monday, and the first week of a year is the one which
includes the first Thursday; equivalently, the one which includes the
4th January.
- Julian Ephemeris date
-
A Julian date that is corrected by delta-t.
- Julian calendar
-
The calendar which was introduced in 46 BC by Julius Caesar
and in the later years corrected by emperor Augustus, that has an
average year length of 365.25 years. This calendar was replaced
by the Gregorian calendar in AD 1582.
- Julian date
- Julian day number
-
A day number that is based on the date 1st January 4713 BCE, which is
the starting day zero of a consecutive day counting used in astronomical
computations. The real zero of this date is at 12 o'clock Universal
time (UTC/GMT); the day does not change at midnight, but at noon
Universal time.
- Leap day
-
The 29th February in the Gregorian calendar.
- Leap year
-
In the Gregorian calendar, a leap year is any year which number can be
divided by 4 without a remainder, and years ending in hundreds are no
leap years unless they are divisible by 400. But the Eastern Orthodox
churches compute leap years within the Gregorian calendar by using another
rule; and that, a leap year is any year which number can be divided by 4
without a remainder, and years ending in hundreds are leap years, if a
remainder of 2 or 6 occurs when such a year is divided by 9.
- Legal holiday
-
A day people don't have to work -- as in most companies, and businesses
are closed; like `New Year's Day' on January 1st.
- Lists of commands
- Ranges of commands
-
Produce more than one calendar sheet per program run.
- Local date variable
-
A Gcal date variable, which is defined in a resource file. Is visible only
in this specific resource file, and that file which is included by it.
- Local star time
- Local sidereal time
-
The momentary period which is past between the last upper culmination
of the vernal equinox point in the meridian of the observer's location
(the momentary hour angle of the vernal equinox point), thus the right
ascension of the stars in the observer's meridian at the moment.
- Local text variable
-
A Gcal text variable, which is defined in a resource file. Is visible only
in this specific resource file, and that file which is included by it.
- Long-style option
-
A special --non-standard-- style to write an option,
e.g. `--foo'.
- Lowest culmination point
-
The lowest point below or above the horizontal plane
which transits a celestial body during a day.
- Lunar Arctic Circle
-
The geographical latitude circle that is between about 61.5
and 71.9 decimal degrees, and the geographical pole.
- Lunation
- Synodic month
-
The mean time between two consecutive New Moon phases.
- Maghrib prayer time
-
The forth Islamic prayer time. Begins at sunset, and ends at the beginning
of the Isha prayer time.
- Magnitude unit
-
Is used to define the brightness of a star, and is a non-metrical value
(Latin term magnitudo, abbreviated m). The difference
between two consecutive magnitudes is 1 to 2.512. Therefore, a star
with the brightness of 1m is 2.512 times brighter than
a star of 2m. A negative magnitude denotes a very bright star,
for example almost -27m for the Sun, whereas the hardly visible
planet Pluto has a magnitude of a bit more than +14m. The Full
Moon has a visual brightness of about -12m.55.
- Marking character
-
Single, printable characters which lead and trail
the output text for marking purposes.
- Mean Earth equator radius
-
The mean radius of Earth at the equator is about 6,378.137 kilometer.
- Mean solar time
- Mean solar day
- Mean sun
-
A star day is also known as a mean solar day. Because the Sun
apparently shifts with respect to the vernal equinox point on the ecliptic
due to the Earth's orbit around the Sun, the star day and the true solar day
have a different length. As the true Sun namely moves irregularly through
the ecliptic, a fictitious mean Sun with a symmetrical motion through
the celestial equator is used for deriving the mean solar time.
- Meridian
-
Either a geographical longitude
or an astronomical vertical circle.
- Metacharacters
- Regular expression operators
-
Special characters in a regular expression.
- Midnight height
-
The elevation of a celestial body
as it happen at astronomical midnight time of the celestial body.
- Midnight phase angle
-
The phase angle of a celestial body
as it happen at astronomical midnight time of the celestial body.
- Modifier
-
One or more characters which directly trail a short-style option,
and which define a special mode of operation for this option.
- Morning width
- Rise width
-
The horizontal angular distance between the rise azimuth of a celestial body
and the East direction.
- Nautical twilight
-
The time when the center of the Sun passes a reference
altitude of 12 degrees below a mathematical horizon.
- Negated character list
- Complemented character list
-
Matches any one of the characters, except those in the square
brackets, in a text, that is processed by a regular expression.
- Negative day
-
Those days in the biorhythm in which one or more of the biological cycles have
a negative maximum value. At that time, one's system is said to be in a lessen
state.
- Noon height
-
The elevation of a celestial body
as it happen at astronomical noon time of the celestial body.
- Noon line
-
The straight line which connects the North and the South point.
- Noon phase angle
-
The phase angle of a celestial body
as it happen at astronomical noon time of the celestial body.
- Octal system
-
Base-eight notation, where the digits are
0...7.
- Opposition
-
The Earth is in one line between the celestial body and the Sun, and
therefore, the celestial body is completely visible from the Earth.
In terms of the Moon, this is the Full Moon phase.
- Option
-
A special type of command line argument
which controls how Gcal behaves.
- Orthodrome
-
A great circles arc that is casted between two points on a surface of a
sphere. Is the shortest geodetic connecting line between two points on a
sphere.
- Pattern
-
A pattern is an arbitrary conditional expression against which input is tested.
If the condition is satisfied, the pattern is said to match the input.
A typical pattern might compare the input against a regular expression.
- Phase angle
-
The phase angle states the phase of a celestial body,
i.e. the illuminated fraction of it as it can be seen from the Earth.
- Pipelining
-
The output of a program is used as an input data stream for another program.
- Positive day
-
Those days in the biorhythm in which one or more of the biological cycles have
a positive maximum value. At that time, one's system is said to be in a raised
state.
- POSIX
-
The name for a series of standards being developed by the IEEE
that specify a Portable Operating System interface. The IX denotes
the Unix heritage of these standards.
- Proleptic calendar mode
-
This means, Gcal only uses a definite calendar system during a definite
period, although there was a change to another calendar system in the
historic reality during this definite period.
- Rational number
- Floating Point number
-
This is a number that can have a fractional part.
- RFC
-
RFC is the abbreviation of Request for Comments.
- Redirection
-
The output of a program is sent to another device instead of sending it
to the standard output channel.
- Refraction
-
Refraction is an optical phenomenon caused by the Earth's atmosphere, which
leads to an apparent raising of the location of a celestial body. The
amount of refraction increases with growing air pressure and sinking
temperature and vice-versa.
- Regexp
- Regular expression
-
A way of describing a set of strings.
- Relative time offset value
-
A time offset value which is related to a base time.
- Religious Islamic calendar
-
The astronomically determined Islamic lunar calendar.
- Resource file
-
A file that essentially contains the fixed date entries.
- Response file
-
A file used by Gcal to preload options and commands at program start-up.
A response file may contain options and commands, but no references
to further response files.
- Right ascension
-
The horizontal angular distance between the center of a celestial body and the
hour circle that passes through the vernal equinox point on the ecliptic.
- Rise azimuth
-
The azimuth of a celestial body
as it happen at rise time of the celestial body.
- Rise height
-
The elevation of a celestial body
as it happen at rise time of the celestial body.
- Rise phase angle
-
The phase angle of a celestial body
as it happen at rise time of the celestial body.
- Set azimuth
-
The azimuth of a celestial body
as it happen at set time of the celestial body.
- Set height
-
The elevation of a celestial body
as it happen at set time of the celestial body.
- Set phase angle
-
The apparent phase angle of a celestial body
as it happen at set time of the celestial body.
- Shell
-
The command processor of the operating system. This operating system
program interprets and runs given command lines.
- Short-style option
-
The traditional --standard-- style to write an option,
e.g. `-x'.
- Simple file name
-
A name that denotes a file, whose access-path either does not start
from the root file directory or from the actual file directory,
like `file' or `bar/file'.
- Simple language code information
-
A language code that consists of two-letters like
de for the
German language, as it is defined in the ISO-639:1988.
- Single command
- 3-Month mode command
-
Produce only one calendar sheet per program run.
- Solar Arctic Circle
-
The geographical latitude circle that is between about 66.7
and 65.9 (corrected for atmospheric refraction) decimal degrees,
and the geographical pole.
For computing the different twilight phases, this latitude circle
decreases to about:
-
60.7 decimal degrees for civil twilight.
-
54.7 decimal degrees for nautical twilight.
-
51.7 decimal degrees for amateur-astronomers twilight.
-
48.7 decimal degrees for astronomical twilight.
- Special text
-
A text in a Gcal resource file which is started by a `%' character
and whose purpose is to suppress output of fixed dates in definite cases,
either, or to provide them with particular texts respectively to start
external commands.
- Summer point on the ecliptic
- Summer solstice
- Solstice in summer
-
The Sun's orbit crosses the highest point above the celestial equator
that is passed during a revolution of the Earth around the Sun.
- Standard week number
-
The week starts on the respective starting day of the week, and the days in
a new year that are preceding the first starting day of the week are in the
last week of the previous year, respectively in week zero of the new year.
- Star day
-
The period between two consecutive upper culminations of the vernal equinox
point on the ecliptic in the meridian of the observer's location.
- Starting date
-
A part of a Gcal special text that defines the first
or earliest date at which the fixed date may occur.
- Statute mile
-
A linear measure, one statute mile is equal to 1.609344 kilometer.
- String
-
A chain of characters.
- Switch character
-
An option is defined by a leading switch character, either the `-'
or the `/' character for traditional short-style options, or `--'
for mnemonic long-style options; a command may not have a leading switch
character.
- Text part
-
That part of a Gcal resource file line that contains the fixed date text.
- Topocentric data
-
Observations of celestial bodies that are done from the
surface of the Earth yield in topocentrically based values.
- True solar time
- True solar day
-
A true solar day is the period between two consecutive lower culminations
of the Sun. This entity is taken as the base for deriving the true solar
time (as it is also shown by a sundial during the day).
- True track
- Course angle
-
The course angle gives the direction, which is the vertex of a great circles
arc (Orthodrome) that is casted between two points on a surface of a sphere,
at a meridian (Gcal uses a geoid (rotation ellipsoid) that is calculated
taking pattern from the World Geodetic System, short W.G.S,
that was designed in 1961). Such an arc is the shortest geodetic connecting
line between two points on a sphere. Indeed, the course angles on such an arc
are changing continually, because the circular line that is casted intersects
each meridian with another angle -- except the case, that both co-ordinates
are referring to exactly the same longitude or to exactly the same latitude.
- Twilight
-
The interval of time before sunrise and again after sunset, during which
natural light is provided by the upper atmosphere that does receive
direct sunlight and reflects parts of it towards the Earth's surface.
- Unix
-
A computer operating system originally developed in the early 1970's at
AT&T Bell Laboratories. It initially became popular in universities
around the world, and later moved into commercial environments as a software
development system and network server system. There are many commercial
versions of Unix, as well as several work-alike systems whose source code
is freely available (such as Linux, NetBSD,
and FreeBSD).
- Vernal equinox point on the ecliptic
-
The point where the ascending Sun's orbit intersects the celestial equator.
- Whitespace character
-
For example Tab, Space, Form-feed and similar characters.
- Winter point on the ecliptic
- Winter solstice
- Solstice in winter
-
The Sun's orbit crosses the lowest point below the celestial equator
that is passed during a revolution of the Earth around the Sun.
- Word
-
A sequence of one or more letters, digits, or underscores (`_')
in a regular expression.
- Zuhr prayer time
-
The second Islamic prayer time. Begins after the astronomical noon time
of the Sun, and ends at the beginning of the Asr prayer time.
