A data transmission of the videotex type in which coded information can be transmitted from a central information store 10 to a plurality of terminals 14. The coded information includes groups of bits representing characters and groups of bits representing control codes. In the transmission technique used in the system a character attribute can be represented by a display control code which is transmitted in association with a cursor backspace code. By using this technique characters of different attributes can be displayed without a space being required between the characters on the display.