As the K-map reveals W, X, Y, Z are the input lines to the device and D0 to D9 are the output lines which get activated depending upon the input combinations. As seen from k-map for W, X, Y, Z from 0000 to 1001 we have D0 to D9 outputs activated respectively. This operation is performed by BCD to Decimal decoder. Also it is called as 1 off 10 decoder, as only 1 of 10 output line is high.