1. A display device, particularly for planning purposes comprising board means having an approximately plane display surface, a plurality of electrical conductors being arranged on or embedded in the said board, said conductors defining a pattern of perpendicularly crossing coordinates, said conductors being isolated from each other, said board having at least one hole at each crossing of said conductors, leading to both conductors adjacent said crossing, and comprising further a plurality of display elements, said display elements having a housing including a pattern of LCD elements for displaying purposes to be observed on a front side of said housing, and a micro processor including a programmable memory, said micro processor being adapted to control the LCD elements, said housing including further at least one pin extending from a rear side of said housing, said pin being adapted to be inserted in one of said holes to releasably retain said display elements on said display surface of said display board, said pin including at least one conducting portion contacting said conductors adjacent their respective crossing, said conducting portions being connected to said micro processor, and computer means coupled to the plurality of conductors, said computer being adapted to be connected to the individual conductors on or in said display board and to communicate with the display elements on said display surface if the pin is contacting said conductors at the respective crossing in order to interrogate the position of the display element and the contents of said memory thereof and/or to program said memory.