Display apparatus with facility for underlining and striking out characters

Claim 1

Display apparatus for displaying an image of a data character with a line associated therewith, comprising: data source means for producing a set of data for a predetermined number of times, said set of data including a data character and an attribute character accompanying the data character and including line data specifying that an image of the data character is to be displayed with an associated line; display signal generator means for receiving the data character in the set of data for the predetermined number of times, said display signal generator means being operative in response to receiving the data character for the predetermined number of times to produce a set of display data signals corresponding to the data character, the number of display data signals in the set being equal to the predetermined number of times that the set of data is produced by the data source means, each of said display data signals comprising a series of a predetermined number of bits; first circuit means having a set of storage locations equal in number to the number of bits in each display data signal produced by the display signal generator means, an additional storage location following the aforesaid set of storage locations and an output, said first circuit operative to receive and store in the set of storage locations therein the bits of display data signals produced by the display signal generator means; second circuit means coupled to the first circuit means and operative when the bits of each display data signal are stored in the set of storage locations of the first circuit means to cause a special bit to be applied to and stored in the additional storage location of the first circuit means; third circuit means coupled to the first circuit means and operative to produce clock signals for clocking the bits of display data signals stored in the set of storage locations of the first circuit means to the output of the first circuit means and, as the bits of each display data signal stored in the set of storage locations of the first circuit means are clocked to the output of the first circuit means, to clock the special bit in the additional storage location along the set of storage locations of the first circuit means thereby to establish a series of said special bits in the set of storage locations; display means coupled to the output of the first circuit means and having a character display area defined by a plurality of display lines equal in number to the number of display signals in a set of display data signals; fourth circuit means associated with the display means and operative to produce a signal corresPonding to a predetermined one of the display lines of the display means; fifth circuit means coupled to the data source means and operative to receive and store therein, for the predetermined number of times that the set of data is produced by the data source means, the line data of the attribute character; sixth circuit means coupled to the first, fourth and fifth circuit means and operative in response to the storage in the fifth circuit means of the line data of the attribute character and in response to a signal produced by the fourth circuit means corresponding to the predetermined one of the display lines of the display means to prevent the first circuit means from receiving a display data signal from the display signal generator means and, instead, to enable the first circuit means to be clocked by the third circuit means thereby to permit the series of special bits established in the set of storage locations of the first circuit means to be clocked to the output of the first circuit means, said series of special bits thereby replacing a display data signal produced by the display signal generating means; said display means being operative to receive the bits of each of the display data signals and the bits of the series of special bits clocked to the output of the first circuit means, and in response to the bits of each of the display data signals to produce in the character display area thereof a portion of an image of the corresponding data character during a corresponding one of the display lines and in response to the series of special bits to produce in the character display area thereof an image of a line during the aforesaid predetermined one of the diaplay lines, the composite image thereby being that of the data character with a line associated therewith.