You need to design a combinational circuit to find the 9's complement
Question: Design a combinational circuit with four input lines that represent a decimal digit in BCD and four output lines that generate the 9's complement of the input digit.
Provide a fifth output that detects an error in the input BCD number. This output should be equal to logic 1 when the four inputs have one of the unused combinations of the BCD code.
Try to reduce the amount of IC's used.
I cannot seem to get this to work for some reason could somebody provide me the answer of this question?