Note: Descriptions are shown in the official language in which they were submitted.
37
The invention relates to a process for the xepresent-
ation of cont~ol symbols on a scxeen of a display device which
contains a page store which can store code words assigned to
alphanumeric and/or graphic characters to ~e displayed on the
5 screen and control symbols which determine properties of the
characters, a keyboard being provided by which the code words
assigned to the characters and the control symbols can be input
into the page store, and an image control unit together with
a character generator which controls the representation of the
characters on the screen.
With the telecommunications service "tele-screen text"
(Video-tex-Interactive), it is possible to call up data stored in
a central unit via a telephone line for display on a television
set. The items of data are represented on the screen of the
television set which serves as a display device. It is possible
to represent alphanumeric characters and/or patterns composed of
graphic characters.
Presenters of information have available to them editing
devices by means of which the items of data are prepared in the
form of screen contents. The screen contents are then transmitted
to the central unit, whereupon they can be called up by
subscribers.
One screen content is referred to as one page. For
example, a page may contain 960 character arrays which are
~5 arranged in 24 rows each comprising 40 character arrays. In
the case of the representation of alphanumeric characters, one
character is represented in each character array. The character
array ma~ consist, for example, of 8x10 or 8x12 image points, by
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which the individual characte~s are represented. Graphic patterns
are represented hy ~es~ectiye characte~ ~rXays each containing
one graphic character co~posed of 2x3 graphic Ple~ents. The
graphic patterns are composed from the combinations of light
and dark graphic elements in the various colours, and it is not
possible to change the colours within one character array.
The display device contains an image control unit which
controls the representation of the characters on the screen.
The image control unit contains a character gene.rator which
stores a predetermined supply of alphanumeric and graphic
characters. With the use of code words which are stored in a
page store and which represent the addresses of the character
generator, data words assigned to the image points of the
characters or to the graphic elements are read out from the
character generators and fed to a display unit which contains the
screen.
The properties of the characters which can be
represented are determined by control symbols, which are likewise
stored in the form of code words in the page store. The control
symbols indicate, for example, in which colour the characters
are to be represented, whether the characters are to be
represented in a flashing or non-flashing manner, and whether at
normal height or at double height. In the case of serial coding
of the characters and of the control symbols, each position on
the screen is assigned one zone of the page store provided for
a code word. If a storage zone contains a code word of a control
symbol, generally no character is represented at the corresponding
position on the screen. A manner of assignment of code words to
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characters and to control symbols is described in respect o
serial coding, for ex~mple, in the magazine 'IFunkschau'' (1977),
Vol. 18l pages 78-82.
In the case of parallel coding, ~he number of the
binary characters of the code words assigned to the characters
which can be represented is increased, so that each character
can be accompanied by a control symbol forming accompanying
information. In this case the gaps provided for the control
~ symbols are omitted, and characters can be represented anywhere
on the screen. It is also possible to combine parallel coding
with serial coding.
As the control symbols are not displayed in the normal
page content, and therefore in the case of serial coding are
indistinguishable from an "interspace" symbol on the screen, if
the screen content must be sat up or amended it is not readily
possible to recognise the positions of any control symbols which
have already been stored~
It would be conceivable, following the actuation of a
corresponding key on a keyboard provided for the setting up or
processing of the screen content, to display a special symbol,
for example the write mark, at every position at which a
control symbol is stored. If a plurality of control symbols
are stored consecutively, again it is impossible to recognise
the position of a specific control symbol, for example, so that
only that control symbol is amended.
It is also already known to display a text which
characterises a control symbol in an additional display row at
the lower edge of the screen whenever the write mark is
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positioned on the screen at a position to which a control symbol
is assigned. In this way it is possible to recognise the
position of a control symbol which is to be modified. However,
if the control symbol is firstly operative at another position,
5 it is firstly necessary to find this control symbol by means of
the write mark. Furthermore, a relatively high circuitry outlay
is needed, since the additional display row must be represented
on the screen.
One object of the present invention is to provide a
process whereby it is possible to determine that point of the
screen of a display device which is assigned to a speciiic control
symbol in a simple and Very rapid fashion.
The invention consists in a process for the
xepresentation of control symbols on a screen of a display
device which contains a page s~ore which can store code words
which are assigned to alphanumeric and/or graphic characters
to be displayed on the screen and control symbols which determine
properties of these characters, a keyboard being provided by
means of which the code words assigned to the characters and
control symbols can be input into the page store, and an image
control unit being provided together with a character generatcr
which controls the representation of the characters on the screen,
said process being such that actuation of a keyboard switch
assigned to control symbols causes special symbols which
characterise the control symbols in question to be represenced
at all relevant positions on the screen assigned to a control
symbol in the page store.
The process proposed in accordance with the invention
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1~9S~37
has the advantage that the setting up, correction and up-dating
of a screen content can be carried out simply and Yexy rapidly,
since it is possible to directly display those positions of the
screen which are assigned to the individual control symbols.
In order to achieve a clearly defined assignment of
any represented characters to the related control symbols, it
is advantageous to represent the alphanumeric and/or graphic
characters during the representation of the special symbols.
Under certain circumstances it can also be advantageous to block
the representation of the alphanumeric and/or graphic characters
during the representation of the special symbols.
In order to be able to indicate on the screen the
function of the control symbol to the user, it is advantageous
for the representation of the special symbols on the screen to
be accompanied simultaneously by a representation of texts
characterising the corresponding control symbols, in an additional
display row. For example, simult~neously to the representation
of the special symbol "Bl", by way of text the word "flashing"
; is displayed in the additional display row.
A further character generator~ or an elaboration of
the character generator already provided, is unnecessary if the
special symbols consist of characters which are stored in the
character gen~rator and which are represented in a special
manner. It is expedient to use as special SymbO15 those
alphanumeric characters whose code words are largely identical
to the code words of the control symbols The representation
can be effected by interchanginy the colour of the chaxacter with
that of the background, for example. It is also possible to
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provide the character with an underline in order to distinguish
it from the noFmal alphanumerical characters which can be
displayed.
The function of the control symbol can also be
indicated to the user on the screen by the use of special
symbols consisting of ~urther characters which indicate the
~unction of the corre~ponding control symbol mnemo-technically
in abbreviated form.
An advantageous embodiment of a circuit arrangement
`-10 for carrying out the proposed process comprises a switching
stage which is supplied by the keyboard with a signal during the
representation of the points of the screen assigned to the control
symbols, and is effective during the read-out from the page
stors of a code woxd ass~gned to a control symbol to supply the
image control unit with a signal which triggers the representation
of the special symbol on the screen.
If the special symbols consist of characters which
indicate the function of the control symbols mnemo-technically
in abbreviated form, it is advantageous to provide a further
character generator, which stores data words assigned to the
special symbols, and which emits the data words to the image
control unit when code words assigned to the control symbols
are read out from the page store.
The invention will now be described with reference to
ihe drawings, in which:-
Figure 1 is a set of diagrams illustrating a portionof a display row on a screen and corresponding zones in a page
store;
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Figure 2 is a set of diagralns illustrating a portion
of a further display xow: ~n the screen and the related storage
zones in the page storei
Figure 3 is a set of diagrams illustrating portions
of another display row on the screen; and
Figure 4 is a block schematic circuit diagram of one
exemplary circuit arrangement for the implementakion of the
proposed process.
In the display ~ow represented by row a in Figure 1,
it has been assumed that alphanumeric characters "A", "B" and
"C" are represented in red, and to be in flashing form, whilst
a graphic character G is repres~nted in green and flashing form.
The corresponding code words for the alphanumeric characters
"A", "B" and "C" and for the graphic character G, together with
their assigned control symbols, are all represented in the
portion of the page store represented by row b. The code words
are stored in binary coded ashion, but for reasons of clarity
in the drawing they have been reproduced in the form of mnemo-
technical abbreviations and gxaphic representations, which may
be utilised in practical displays. Following a code word for
the symbol "interspace" there is stored in the page store one
code word for the control symbol "cCred" (alphanumeric character,
red) and one code word for the control symbol "Bl on" (flashing).
Following two further code words for the symbol "interspace",
there then follows the code words for the alphanumeric characters
"A", "B" and "C", followed by the code words for the symbol
"interspace", the control symbols "Gr gn" (graphic character,
green) and "sep Gr" (punctiform graphic character, separated
graphics), and for the graphic character G. The control symbols
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" ~ red" and "Bl on" result in a ~lashin~ representation of the
alphanumeric charactexs '~BC'I in xed~ ~imil~rl~ the control
symbols "Gr gn" and "sep Gr" result in the repxe~entation o~
the graphic character G in green with punctiform elements.
S The same representation on the screen is also achieved
if, as illustrated at row c, the control symbol "sep Gr" is
arranged preceding the alphanumeric characters "AB~". In
any particular case it is only operative at the point a~ which a
graphic character such as G is represented. In the case of
`10 representation on the screen in accordance with the display row
represented in Figure 1 row a, it cannot be recognised where and
in which sequence the individ~al control symbols are arranged, so
that it is not readily possible to correct or to bring up to date
the display row.
In the alternative case represented in Figure 2 it has
been assumed that the alphanumeric characters "ABC" are not
to be represented in flashing form, and that the graphic character
G is to be still flashing, but composed of contiguous surface
( , elements, as shown in Figure 2, row a. The change can be made
by inserting the control symbol "Bl off" (stop flashing) prior
to the alphanumeric characters "ABC", and two control symbols,
"con Gr" (surface~form graphic character, continuous graphics)
and "Bl on", both of which are inserted prior to the graphic
character G, as illustrated in Figure 2, row bD However, if the
positions of the individual control s~mbols are known, it is
possible to reach the same result by erasing the control symbols
"Bl on" and "sep Gr" from the array shown in Figure 1 row c and
inserting the control symbol "Bl on" prior to the graphic
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charactex 5, to obtain the content sho~m in Figure 2 row c.
In order to be able to change the store content
represented at row c of Figure 1 into the store content
represented in row c of Figure 2, it is necessary to determine
the positions of the control symbols. In accordance with the
process, a key on the keyboard is operated which results in the
representation of positions of the scxeen assigned to the control
symbols by means of special symbols. During the representation
, of the special symbols it i~ possible to block the representation
of the other characters.
As illustrated in Figure 3 at a, the control symbols
are represented by special symbols which contain alphanumeric
characters. In order to be able to distinguish these selected
alphanumeric characters from the basic alphanumeric characters
normally to be represented on the screen, they may be represented
inversely, that is to say with the background and foreground
colours interchanged, or with an underlining. No further
character generator is needed for the display device if the
( special symbols consist for example of those alphanumeric
characters whose code words differ as little as possible from the
code words of the corresponding control symbols. For example
the code word for the control symbol "Bl on" differs from the
alphanumeric character "H" only in the highest value binary
character. In order to simplify the assignment of the special
symbols to the control symbols for the user it is possible to
display an explanatory text relating to the called up control
symbols in known manner in an additional display xow on the
screen.
Another possibility as regards the formation of the
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special symbols consists in that, as shown in Figure 3, row _,
mnemo-technical abbreviations of the control symbol are
represented at the appropriate position. For this purpose,
however, it is necessary to provide an additional character
generator, or to extend the existing character generator, as two
alphanumeric characters are arranged in each o~ these character
positions.
Following the actuation of the corresponding key on
the keyboard, all the control symbols are displayed simultaneously
on the screen when employing the proposed process. In the event
of a change in the screen content the user can now position the
write mark at the appropriake position on the screen and modify
the control symbol in question in a simple manner.
The display device which is illustrated schematically
in Figure 4 is provided for the "tele-screen text" telecommunications
service, and is connected via a modem M to a telephone line F. The
modem M is Gonnected in known manner to a telephone handset FA.
Using the display device, on the one hand it is possible to call
( up items of data via the telephone line F from a central unit and
to represent these items on a screen BS of a display unit AE,
and on the other hand it is possible to construct or correct the
screen contents by means of a keyboard TA~ and then to transfer
these revised contents via the telephone line F to the central
unit. Further screen contents can be stored in a peripheral
store PS.
The display device contains a control unit ST which
controls the time sequence, and normally contains a micro-
processor. The control unit ST is connected to the keyboard
TA. In addition the display device contains a page s~ore SP
~ ~ ~S'7~7
which stores code word~ CW of at least one screen content, i.e.
of one page. The page store SP is followed by an image control
unit BST which emits video-signals to the display unit AE in
dependence upon the content of the page s~ore. The image control
unit BST contains a character generator Z which is addressed by
code words CW and which contains data words assigned to the
forms of the characters which are to be represented. Furthermore
the display device contains a switching stage shown enclosed in
a chain-dashed rectangle, which makes it possihle to display all
the control symbols of a page stored in the page store SP.
This switching stage S contains a further character
generator Zl which stores special symbols which contain mnemo-
technical abbreviations~ as illustrated in row b of Figure 3.
Following the actuation of an appropriate switch on the keyboard
TA, this character generator emits a signal Sl to the switching
stage S.
The signal Sl is fed to A first input of an AND gate
whose second input is supplied with the code words CW and whose
output is connected to the address input of the character
generator Zl. If, during the representation of the screen content,
the code words CW of the characters and of the control symbols
are read out from the page store SP, by means of the character
generator Z in the image control unit BST the characters are
displayed on the screen BS. ~hen the code words CW assigned to
a control symbol are read out irom the page store SP, the
character generator Z contains no corresponding data words so
that it does not emit any video-signals. Since the data words
CW are fed via the AND gate U to ~he character generator Zl and
the latter contains special symbols which represen~ the control
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symbols, at the tLme ~f the read-out of the corresponding
code words CW from the page stoxe SP, the data words assigned
to the special symbols are read out from the character
generator Zl and fed, by way of signals S2, to the image control
unit BST. This produces corresponding video-signals which it
emits to the display unit AE in order to represent the special
symbols on the screen.
If si~ultaneous representation of the aphanumeric
characters and the gxaphic characters is undesired, the signal
Sl can also be fed to the image control unit BST where it will
block the character generator Z.
With the aid o~ the proposed process, the described
arxangement makes it possible to characterise not only the
control symbols but also those points of the screen BS at which
graphic patterns are to be represented in punctiform fashion,
by the same arrangeme~t as that for the alphanumeric characters.
These graphic patterns are usually stored in a write/read s~ore
from where they are called up under predetermined addresses
(DRCS, dynamically redefinable character set). The addresses
of these patterns are then stored at the corresponding positions
in the page store. If these addresses are called up by means
of the keyboard, the positions on the screen BS at which the
corresponding graphic patterns are represented are displayed.
