Let us design a 4bit binary to BCD code converter. As the 4 bit can represent 0 to 15, we can draw the conversion table as follows,
Here, B5 bit represents MSB of decimal number and B4, B3, B2, B1 represents 4 bit binary equivalent of LSB of decimal number.
From, above conversion table, we can write SOP form for different bits of BCD code.