GB2151888A - Display tabulation setting - Google Patents

Abstract

A display tabulation apparatus includes a data display storage register 2, a cursor identifying the location along a character line of the next character to be entered, a tabulation position storage register 9 for storing presettable tabulation positions along a character line, and comparator means 24 for comparing the instantaneous position of the cursor with the next tabulator location set into the register to produce a control signal for causing displacement of the cursor to the next preselected tabulation position upon execution of demand for a tabulation operation. <IMAGE>

Description

SPECIFICATION Display tabulation setting This invention relates to display devices and more particularly to hand holdable terminals which incorporate a display screen and means for controlling the introduction and deletion of material to be recorded by the display.

Usually the hand held terminal is connected with or is adapted for connected with a so-called "host unit" which can comprise inter alia a visual display system.

When using a hand held terminal it is frequently necessary to be able to flag, mark or otherwise identify the beginnings and ends of a message or selected portions of a message, or the positions at which portions of data are required to be positioned with respect to the overall display area.

Such a requirement clearly arises in connection with the presentation of information in tabular form.

The presentation of information in tabular form calls for a user controllable facility called tabbing or tab-setting and is somewhat analogous to the setting of the tabular stops on a typewriter.

In the case of tab-setting on a visual display unit it is known to provide a tab register which is operationally connected with the visual display unit so as to operate in synchronism therewith whereby when it is required to set a tab in the display of the visual display unit the tab register is used.

It will be understood that each tab set into the display involves a character space on the display so that for the purposes of providing a general tabbing facility a large amount of visual display space would need to be reserved merely for the tabbing facility. It is also known to effect tabbing on visual display unit screens by specifying a protected area in which the host processor unit is used to set codes into a buffer store associated with the screen, i.e. to mark the beginning of and the end of each protected area of the screen. In practice, these protected areas are used to accommodate information which it is desired continuously to depict on the screen whilst data - on the remaining areas of the screen may be augmented, moved or altered as required.

It is convenient at this point to recall the purpose of the tabbing operation. In broad terms tabbing is concerned with the setting of locations along a line at which groups of characters should commence. In general terms tabbing is of importance in setting margins or establishing the positions of characters which it is required to set out in vertical columns.

In practice, facilities are provided to enable the presetting of the above mentioned start and stop locations. Conventionally a key, commonly called the tab key is provided on a conventionally provided data input keyboard, or the like whose operation is so related to the tabbing facilities that operation of the tab key automatically causes the next character to be displayed to be placed at the next one of the predetermined locations - that is the position of the next character to be entered is automatically shifted to the next selected tab location.

According to the invention there is provided a data display terminal including a data display data stor age register, a cursor facility for identifying the location for the next data character to be presented on a data display; a tabulation position storage register for storing presettable tabulation positions with respect to a line of characters on the display; means for addressing the tabulator position register to produce a signal indicative of the address of the next required tabulation position along a line; and comparator means for comparing the instantaneous position of the cursor with the signal indicative of the next tabbing position to produce a control signal for causing displacement of the cursor to said next tabbing position.

For a better understanding of the invention reference will now be made to the accompanying drawing the figure of which is a schematic representation of a circuit arrangement for facilitating tabbing operation on a hand holdable terminal. In the drawing a dashed line rectangle 1 represents a display screen buffer unit of a hand holdabletermin- al assembly. The unit including a buffer store 2 into which data information is written on a byte-by-byte basis by way of a keyboard 3, and from which data is displayed on display 4 by way of databus.

The buffer unit can be conveniently regarded as a virtual screen which comprises a field of RAM into which symbols i.e. characters are written on a byte-by-byte basis, across the line length of the field of display.

The display screen has associated therewith a cursor pointer 6 which defines the location of the next character to be inserted into the display whereby in use depression of the associated character entry key 7 of the keyboard 3 will enter the desired character and will cause the cursor pointer 6 to increment one character space or byte to define the next character position.

Before discussing the circuit arrangement in detail a tabbing operation will be considered in general terms with respect to the drawing.

In order to effect a tabbing operation the movement of the display cursor pointer 6 has to be modified so that operation of the tabbing key will cause the cursor pointer 6 to move to the next predetermined tab location along the line of characters. In other words the cursor is caused, on depression of a tabbing key 8 provided on the keyboard 3 to move to the next one of a series of tabulation location addresses corresponding to preset tabulation locations. In practice, the tabbing locations are defined in relation to the beginning of a line of characters.Thus all of the possible tab locations have addresses referred back to the beginning of a line rather than from tab position to tab position, so that the bytes to which a given set of tabulation steps correspond can be identified by a set of displacements of the cursor pointer 6 from the start of a line of characters of the display 4.

These displacements are stored in a tabulation location address register or table 9 having address locations 10 for containing one entry for each tab location defined or preset and are arranged in ascending order i.e. cursor pointer displacement distance from the commencement of the associated character display line.

With this arrangement when the tabbing key 8 is operated the cursor pointer symbol 6 is caused, temporarily to disappear from the screen (i.e. blacked-out) of the display 4, the particular line in which the characters are being entered is identified and the next tabbing address (i.e. from the start position of the identified line) is established from the tab location table 9. This address is used to move the cursor pointer 6 to the required tab setting and the cursor pointer is then enabled to provide a visual indication of the next character position i.e. at the selected tab location.

The insertion of characters into the screen will proceed from the tab selected location and will continue predefined tab position - in advance of the instantaneous cursor pointer setting.

The circuit arrangement of the drawing will now be discussed in greater detail.

As has been mentioned the tabbing locations for the display required can be preset in to the tabbing loction register 9 by means of a tab set control signal which may be produced locally by operation of the tab setting key 8 provided on the keyboard 3, the key 8 being functionally connected with the tabbing location register 9 by a control connection 11.

Alternatively, the tab setting function can be effected by way of control signals produced by a microprocessor or other processor unit 12 with which the hand held terminal assembly is functionally connectable as indicated by connection 13.

The tab location address register 9 also arranged to map onto storage facilities 14 associated with the processor unit 12 - this is represented by the connection 15.

The buffer unit 1 incorporates an address register 16 which serves to store the address of the cursor pointer 6 in the screen buffer. In addition, to the address register 16 the unit 1 includes a further register 17 which is intended to store the position of the cursor pointer 6. This further register 17 essentially comprises two parts, a first part 18 which stores the instantaneous line number of the buffer lines into which characters are being entered or are to be entered, a second part 19 for defining byte-bybyte positions along the line. In other words - as the hand held terminal is used to accept data into the data buffer store 2 as a data input key (i.e. key 7D) is operated.The register 19 is automatically incremented to advance the cursor pointer 6 along the selected line, this is schematically represented by the control connection 20 connecting the register 19 with the display 4.

In addition, the operation of a data input key at the end of a line simultaneously increments the line register part 18 and resets the character register part 19 to beginning of a line. Thus the instantaneous character position within the line is effectively stored in the second part 19 of the register 4. The interrelation of the register parts 18 and 19 and the register 16 with the address register is represented by the connections 21,22.

A comparator unit 24 is provided for comparing by way of connection 25 the instantaneous character address, i.e. the address value of the register part 19, with the preset tabbing locations of the tabbing register 9, an output 26 of the latter being connected to the comparator 24, whereby the latter is able to compare the instantaneous tabbing register output with the output from the character position part 19 of the register 17. When the tab command is present, the comparator 24 essentially produces two outputs on an output line 27 - a first whenever the output from the tabbing register exceeds that from the register part 19, and a second output when the tabbing register output is equal to that from the register part 19.Initially, the tab cursor pointer 6 steps from a least value address along the line until a tab address is found which is greater than the current character register address. Once the required next tab setting has been set, the character cursor pointer 6 automatically steps on until the second of the above mentioned conditions prevail - that is to say the address position for the next character to be entered co-incides with the present tab address. In other words following the re-positioning of the cursor pointer 6 to the required tab position, the next operation of a data key will cause the next data item to be placed at the cursor pointer position which is at the selected tab position.

It will be understood that the sequencing of the system required that the microprocessor shall allow the tab function control of the cursor pointer 6 (i.e.

breaking out) to be removed before the cursor stepping on to the selected tab position is applied to the register part 19.

Claims (4)

1. A data display terminal including a data display data storage register; a cursor facility for identifying the location for the next data character to be presented on a data display; and a tabulator position storage register for storing presettable tabulation positions with respect to a line of characters on the display; means for addressing the tabulator position registerto produce a signal indicative of the address of the next required tabbing position along a line; and comparator means for comparing the instantaneous position of the cursor with the signal indicative of next tabulation position to produce a control signal for causing displacement of the cursor to said next preselected tabulation position upon execution of a demand for a tabulation operation.

2. A data display terminal as claimed in claim 1 and characterised in that the cursor facility includes a two-part storage register, of which a first part serves to define the instantaneous line number of the data to be displayed, and a second part serves to define the instantaneous character position by means of a cursor pointer.

3. A data display terminal as claimed in claim 1 or 2, and in which the comparator means is arranged to produce a first output when the tabulation location address is greater than that of the cursor position such that on effecting tabbing demand the cursor is caused automatically to advance to the selected tabulation location whereby a second output is produced indicative that the address position for the next character to be entered into the display coincides with the selected tabulation location.

4. A data display terminal constructed and arranged to operate substantially as hereinbefore described with reference to the Figure of the accompanying drawing.