Subtração em BCD

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Step of 3 2.032E The following is the procedure that must be followed while doing subtract Binary Coded Decimal (BCD) numbers: 1. Determine the ten's complement of the subtrahend and then add it to the corresponding minuend. 2. If the resultant is less than 9, take ten's complement of the result and append negative sign to the final result. 3. If the carry occurs then just discard it. 4. Else check whether the result is greater than 9, if it is so add binary equivalent of +6 to the result, discard the carry if it occurs in this addition. Now apply these rules to the following problems. Determination of subtraction 8-3 Binary Coded Decimal equivalent of 8 is 1000 Ten's complement of 3 is 10-3=7 and Binary Coded Decimal equivalent of 7 is 0111 Add the Binary coded decimal of 8 and ten's complement of 3. 1000 0111 1111 Result has no carry but it exceeds the value 9. So, add binary coded decimal equivalent of 6. 1111 0110 10101 Carry occurs in the addition and hence discard it. Then the result is 0101 which is Binary coded decimal equivalent of the decimal number 5 Therefore, the result for the arithmetic operation 8-3 is 5 Step of 3 Determination of subtraction, Binary Coded Decimal equivalent of 4 is 0100 Ten's complement of 8 is 10-8=2 and Binary Coded Decimal equivalent of 2 is 0010 Add the Binary coded decimal of 4 and ten's complement of 8. 0100 0010 0110 Result has no carry but it is less than 9, so find the ten's complement of 0110 by subtracting the binary number 1010 from 1010 0110 0100 0100-4 Therefore, the result for the arithmetic operation 4-8 is -4 Step of 3 Determination of subtraction, Binary Coded Decimal equivalent of 5 is 0101 Ten's complement of 9 is 10-9 = 1 and Binary Coded Decimal equivalent of 1 is 0001 Add the binary numbers, the Binary coded decimal of 5 and ten's complement of 9. 0101 0001 0110 Result has no carry but it is less than 9, so find the ten's complement of 0110 1010 0110 0100 Taking ten's complement denotes the negative sign of the result just like one's complement and two's complement representation of binary numbers. According to the fourth statement append negative sign. Therefore, the result for the arithmetic operation 5-9 is -4 Determination of subtraction, 2-7 Binary Coded Decimal equivalent of 2 is 0010 Ten's complement of 7 is 10- = 3 and Binary Coded Decimal equivalent of 3 is 0011 Add the binary numbers, the Binary coded decimal of 2 and ten's complement of 7. 0010 0011 0101 Result has no carry but it is less than 9 and so by second rule find the ten's complement of 0101 by subtracting 1010 from 0101 1010 0101 0101 0101-5 According to the second statement append negative sign to the result, -5 Therefore, the result for the arithmetic operation 2-7 is -5