1. A method for designing a circuit using graphic editor software, comprising: generating a first graphic design file corresponding to a first block diagram created in a graphical user interface associated with the graphic editor software, the first block diagram comprising a plurality of blocks and a plurality of conduits interconnecting the blocks; and generating a block design file in one of a plurality of formats for each of selected ones of the plurality of blocks in the first block diagram, each of the block design files corresponding to an implementation of its corresponding block, wherein the plurality of blocks include fully specified blocks and partially specified blocks; wherein modifications to any of the first graphic design file and the block design files are incorporated into each other under software control.