Video display system

Claim 1

Apparatus for displaying characters including in combination display means capable of producing images on a display surface by selectively writing on the display surface while repeatedly sweeping a raster scanline pattern over the display surface; first memory means for storing digital code words in a plurality of storage positions, each storage position corresponding to a location on the display surface of said display means, and the storage positions being arranged in an array designating the locations on the display surface by first and second orthogonal sets of lines; second memory means for storing character image data in a plurality of storage positions; each of said digital code words being a character code word representing a character to be displayed or being an address code word designating storage positions in said second memory means; data input storage means for receiving and storing a digital code word, or character image data; address input storage means for receiving and storing display location information designating a storage position in said first memory means associated with a digital code word stored in said data input storage means, or storage position information designating storage positions in said second memory means associated with character image data stored in said data input storage means; memory access storage means for receiving and storing a first indication when a digital code word is received and stored in said data input storage means and display location information is received and stored in said address input storage means, and for receiving and storing a second indication when character image data is received and stored in said data input storage means and storage position is received and stored in said address input storage means; said first memory means being operable to receive a digital code word from said data input storage means and the associated display location information from said address input storage means and to store the received digital code word in the storage position designated by the received display location information when enabled by a first indication from said memory access storage means; said second memory means being operable to receive character image data from said data input storage means and the associated storage position information from said address input storage means and to store the received character image data in the storage positions designated by the storage position information when enabled by a second indication from said memory access storage means; first memory readout means for reading out digital code words from the storage positions of said first memory means designating locations in a line of the first orthogonal set in sequence for each tracing of a scanline; second memory readout means coupled to said first memory means for reading out character image data from the storage positions in said second memory means designated by an address code word read out of said first memory means; character data generating means coupled to said first memory means and operable in response to a character code word being read out of a storage position in the first memory means to generate character image data pertaining to the character represented by the character code word; and output means coupled to the character data generating means, the second memory means, and the display means; said output means including character data selection means for selecting character image data from the character data generating means in response to a character code word being read out of said first memory means and for selecting character image data from the second memory means in response to an address code word being read out of said first memory means; said output means being operable to cause the display means to write the selected character image data on the display surface at the location on the display surface corresponding to the storage position of the digital code word in said first memory means.