Appendix 1 : Package Classes.
'Three-dimensional' - a term used to describe attempts to draw a
three- dimensional object such as a curved surface or xyz graph on a
two-dimensional screen or piece of paper. Also called 'two-and-a
Four-dimensional' - a 3D diagram in which colour is used
to depict the variation of a fourth variable.
Standard paper sizes: A4 is 297mm by 210 mm; A3 is 420mm by
297mm with sizes A2, A1 and A0 progressively doubling. A5 is
210mm by 148mm
A chart in which the area of interest is shaded in solid colour: useful
for capturing attention but should be used sparingly for best effect.
The American Standard Code for Information Interchange - a
standard for the representation of textual characters held in a
computer system. For example the ASCII value for 'A' is 65, or
01000001 in binary.
A 'horizontal histogram', in which data values are represented by
horizontal bars. Not used widely, but particularly effective where
each individual data point has to be named. See also column chart.
See cluster chart.
A general term for methods of presenting data in a formal,
structured fashion - such as a line graph, bar chart, pie chart or
histogram. See also "creative graphics".
A measurement system for defining the position of a point
with respect to two (or more) straight axes at right angles to each
other. This is the commonest coordinate system, the main alternative
being polar coordinates
CGM 'Computer Graphics Metafile', an ISO standard by which
information can be stored in a computer file, in which form it can be
transferred and reconstituted. CGM is more commonly used for
transferring graphical images between software packages than for
sending it to output devices such as plotters.
A general term indicating any drawing, graph, image, text, or
combination of these elements.
CHEST Combined Higher Education Software Team. CHEST arranges and
administers software deals on behalf of the UK academic
community. The CHEST Software Directory is available on-line
through the NISS Gateway, and in book form.
Collections of graphic images or symbols stored in computer form
which can be readily incorporated into more complex diagrams,
documents or presentations to enliven their appearance. Clip art
libraries are available to cover most everyday items and many
specialised ones. Care should be taken to observe any copyright
restrictions when using clip art.
A form of chart suitable for depicting data which only falls into a few
restricted categories, such as 'normal', 'high' or 'low'. The x axis is
then usually descriptive rather than numeric. Used particularly in
medical and biological work.
A chart in which data values are represented by vertical columns:
histograms are a specific class of column chart used in statistical
work. See also bar chart.
A method for depicting 3D data such as the heights of a landscape7
in general, for any measurements which are a function of two
other, independent, variables. Thus each point is specified by three
measurements, two for its position (x,y) and one for its actual value
(z). An Ordnance Survey map isia contour chart.
A general term for informal and unstructured graphical presentation,
not usually representing any pre-existing data. Common examples
are drawings and diagrams produced by hand. See also "business graphics".
The attempt to find a pattern in data by drawing a line through a set
of points so that it goes as close as possible to all of them. This
could be a straight line but is more generally a curved one, ideally
with an underlying equation which would help to analyse the data.
See "Dynamic Data Exchange".
A software module which accepts input in some general form and
converts it into specific instructions which are sent to a specific
printer, plotter or other output device. For example many graphics
packages and word-processors generate their output in device-
independent form and rely on specific device drivers to produce the
actual output. In this method of working every device must have its
own specific device driver.
The operational mode of many graphics and word-processing
packages, which do not produce their output in a form which can be
sent to any output device (such as a plotter or printer), but which
contains all the necessary information from which a device driver can
generate the required output on information from which a device
driver can generate the required output on a particular device.
A device which converts graphical input into a digital form which
can be manipulated in a computer. It consists of a tablet on which a
diagram can be mounted, and a pen-like stylus which can be traced
around the diagram, producing digital measurements which are fed into the computer.
A graphical device which enables pictorial information to be input to
a computer. It is especially appropriate for line-based pictures (for
example mapping boundaries). The process involves drawing over
each line with a special stylus or mouse device.
The technique of manipulating patterns of dots produced by a printer
to generate more colours or shades of grey than it should be capable
of. For example if a black-and-white printer can print a small box as
a pattern of black and white dots, the overall appearance of the box
will be grey, its precise shade depending on the reladve proportions
of the black and white dots. Similarly a simple colour ink jet printer
can produce various shades of orange from patterns of red and
yellow dots. This is a very effective technique, but the penalty is loss
of resolution in the final image.
A (cheap, noisy and comparatively slow) printing device in which
text and graphics are produced by an array of pins forcing a printer
ribbon against paper. The alternative is a 'non-impact printer' such as
an 'inkjet printer' (relatively cheap) or 'laser printer' (relatively
dots per inch('Dpi')
a measure of the resolution of an output device such as a
computer screen or laser printer, which effectively shows the size of
the dots it uses to generate characters and graphics. The bigger this
number, the smaller the dots and the finer the resolution. For
example, apple mac screens have 72 dpi, and most laser printers
have 300 dpi, with 600 dpi starting to appear in desktop machines.
The very best publications require at least 1200 dpi devices.
dpi Acronym for dots per inch.
A proprietary method of linking the data in one application to a
graphical or other display in another application. When the data is
changed in the first program, the display in the second is updated
automatically, allowing a single master set of data to be used for all
"Envelope-ing" - distorting a graphical image by fitting it into a non
rectilinear shape, or envelope.
Lines which are added to the data points in certain types of graph to
indicate the margin of error in that point - that is, the range within
which it lies. An error bar indicates the range of values when several
measurements are used to generate a single point on a graph, or the
maximum possible error in measuring or calculating the position of
A measure of the capability of, or range of facilities available in, an
item of software or hardware. Modern computer packages and
equipment tend to have much better functionality than older ones,
and expensive ones greater functionality than cheaper ones.
A characteristic style of user-program interface in which the
computer is controlled graphically - by a mouse acting through
windows and icons - rather than by issuing it with textual
commands. See also WIMP.
The ability of a black-and-white printer or screen to display shades
GUI Graphical User Interface, pronounced "gooey". See also WIMP.
hardcopy Output on a permanent medium such as paper, transparency, film or
video, as opposed to temporary output to a computer screen.
histogram A special form of 'column chart', particularly used in statistical
applications, using vertical columns to display the value of the data
point vr the average value of a range of data points in a limited set of
hot link A connection between data in one program and its use in another,
for example allowing data to be changed in a spreadsheet,
whereupon a separate graphics or DTP package - connected to the
first by a hot link - automatically changes its representation of that
'Hewlett-Packard Graphics Language' - a de facto standard language
with which to control pen plotters, which is also accepted by a
number of non- pen devices such as laser printers and electrostatic
( 1) any graphic item, made up of any graphical elements including
text. (2) a precise copy of the contents of a computer's memory,
elsewhere in memore or on a disk.
Printing devices in which text and graphics are produced by an array
of pins forcing a printer ribbon against paper. They tend to be cheap,
but produce low-quality output and are noisy and comparatively
Drops of ink at the paper, typically on a 300 dpi matrix. Results are
almost as good as a cheap laser printer's, though the ink tends to
spread a litde, and will run if it gets wet.
A non-impact printing device which operates in similar fashion to a
photocopier, in which a laser draws the image of a page on a
photosensitive drum which then attracts toner on to the paper, where
it is subsequently bonded by heating. Now the most popular type of
printer for reasonable
Very similar to a laser printer, but using leds (light-emitting diodes)
rather than a laser to create the electrostatic charge on the drum.
Line art A diagram which consists only of lines and text, requiring no
complex grey level or colour shading.
Line chart One of the commonest forms of graph, particularly favoured by
scientists, with data points displayed against X and Y axes and all
the points connected with a single line. The points themselves need
not be shown. Alternatively, all the data points may be shown and a
line dtawn which doesn't necessarily go through them all but which
gives a reasonable 'best fit' to them all.
media Plural of 'medium', referring to the types of material on which
computer output can be stored. The commonest media ase disks
(}tard and floppy), magnetic tape (reel and carhidge), optical disks,
punched paper and punched cards, ordinary paper, photographic
film, video, and semiconductor 'flash-cards'.
metafile A file which contains a description of a picture or set of pictures in a
well- defined, formal manner. This allows diagrams to be transferred
betv-veen different graphics packages, and also allows programs to
ignore the specific details of particular output hardware - but just use
a common 'device- driver' to translate the metafile into printer
Transforming a graphical image into its horizontally reversed form,
as though reflected in a mirror.
mono(chrome) An output device which can only show one colour, though possibly
in several shades. Monochrome printers and some screens tend to be black and white.
Printers and plotters which do not use physical force to transfer ink
to paper, common examples being inkjet, thermal-wax and laser
paired bar chart
A special kind of 'bar chart' which uses horizontal columns in pairs
to emphasise the differences in measurements taken at two different
times, places, experiments etc.
A reasonably cheap type of output device which uses pens to draw
graphic images on paper. It is fine for producing smooth lines and is
therefore the natural way to draw line charts, but it has few colours,
is not sensible for area fill, and is slow for complex drawings.
perspective A technique for making three-dimensional objects look more natural
when represented on paper or screen, by for example making distant
objecls smaller than closer ones, and parallel lines converge in the
An effective method of displaying (preferably no more than) about
six variables, rather Like looking down on a circular apple pie which
has been cut into slices. The size of each slice reflects the size of
A chart on which data points are plotted in polar coordinates rather
than 'Cartesian coordinates'. Each point is defined in terms of its
distance from the centre of a circle and the angle a notional
connecting line makes to the horizontal.
A de facto standard page-description language from the Adobe
Corporation, which is now the most widely used way of sending text
and graphics to printers such as laser printers - many of which now
have postscript interpreters built-in for speed and flexibility.
prepress Final preparation of material to be printed to the highest standards,
probably by an external, professional printer. This includes the
specification of all the fonts and graphics used in a document.
presentation In the normal sense of the word, a presentation is some kind of talk
to an audience, possibly enhanced with visual or audio material. A
'presentation package' runs on a computer to assist with the
production of illustrative material to be used in a presentation, either
in generating such aids as overhead or 35mm transparencies, or
increasingly - used at the presentation itself, with the on-screen
images viewed directly by the audience.
QC chart, Quality control chart. A chart which shows the acceptable range of measurements, perhaps
on some manufactured item or experimental data, on which actual
measurements can be plotted to show whether the manufacture or
experiment is proceeding satisfactorily.
raster The teclmique of building up a graphical image as a series of on/off
or coloured dots along a set of lines on a screen or other output
device. A television set is the commonest form of raster device. In a
laser printer or computer display, for example, the image is built up
by a signal which is swept along each line in succession, and
variously attenuated to produce the required pattern. The alternative
method of producing images is 'vector'.
resolution The fineness of detail which a computer device can detect or
produce. For example a high-resolution screen or printer can show
fine detail, and a high- resolution scanner or digitiser can detect fine
rotation Transforming a graphical image by rotating it about some axis, to
some degree. 'Mirroring' is a special case of rotation.
scanner A device which scans a light across a page of text or graphics and
feeds a digitised representation of the image into a computer for
storage or further processing. Scanners are typically flat-bed (like a
photocopier), rotating- drum, or hand-held. If the image is text,
there are software packages which can convert it from an image to
actual characters which can for example be loaded into a word
scatter chart A classic 'x vs y' graph consisting of two axes, with each data point
marked with its own symbol: like a 'line chart' but without the
site licence An agreement between a software publisher and an educational
establishment which allows software to be acquired at a reduced
price, on condition that it is only used for academic, non-commercial
skewing Transforming a graphical image by distorting it about some axis, to some degree. For example, a square can be skewed into a diamond
subscript, Text which is written on a lower baseline, and usually in a smaller
font, than its surrounding text, as for example the x in lx.
Text which is written on a higher baseline, and usually in a smaller
font, than its surrounding text, as for example the 2 in x2.
A chart consisting mainly or exclusively of text, added graphical
elements including colour, font and background. Text charts are
commonly used on overhead and 35mm transparencies and in
'presentation' packages, for example.
A character design, specifying the shape of all the upper and lower
case characters, numerals and punctuation symbols Different
typefaces are useful in different contexts, for example in running text
or in headlines, and to give an old-fashioned, or conservative, or
modem, or striking appearance. Commonly used typefaces include
times, helvetica and courier. Each typeface is actually a family of
individual 'fonts', each of which represent the typeface in a pardoular
size (such as 12 point) and style (such as bold or italic). The words
'font' and 'typeface' are increasingly - and inaccurately - used
Uniras A large and powerful graphics package available on a range of
computer platforms to enable users to generate most types of
vector A straight line drawn from one point to another point. Vector
devices, of which the commonest type is the 'pen plotter', are
designed specifically to draw or plot vectors, making them ideal for
graphical objects such as line charts which consist only of lines. The
more versatile alternative is a 'raster' device.
"Windows, /images/, Menus and Pointer", or "Windows, /images/, Mouse
and Pull-down menus" This is a graphical interface which makes
access to computers much more straightforward and intuitive than
the main alternative, the command-line interface. The WIMP
interface has been used on Apple Macintosh computers since they
were invented, and are coming into use on PCs through Microsoft
Windows and on Unix and other workstations through the X
A graphical (GUI) interface to a computer's Operating System,
giving the user such features as windows, a mouse and pull-down
menus by which to drive the computer, rather than having to type in
Any computer which can sit on a desk, though usually taken to
indicate amore powerful machine such as those from Sun or Silicon
Graphics, rather than a less powerful PC or Apple Mac.
WYSIWYG "What You See Is What You Get" - the description of systems or
packages which faithfully represent on the screen what a document
will look like when printed.
Appendix 1 : Package Classes.
Virtual Environments Visualisation