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# Decimal Multiplication and Decimal to Binary Conversion Utilizing a Three Input Adder

IP.com Disclosure Number: IPCOM000075039D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 19K

IBM

## Related People

Jackson, RT: AUTHOR [+3]

## Abstract

Decimal multiplication and decimal-to-binary conversion can be rapidly performed through the use of a three-input adder, having input registers R1, R2 and shifting gates S1, S2, S3. Decimal Multiplication.

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Decimal Multiplication and Decimal to Binary Conversion Utilizing a Three Input Adder

Decimal multiplication and decimal-to-binary conversion can be rapidly performed through the use of a three-input adder, having input registers R1, R2 and shifting gates S1, S2, S3. Decimal Multiplication.

In many machines, multiplication is performed by selecting a decimal multiplier digit and decrementing it by one until zero is reached. For each decrement, one multiple of the multiplicand is added to the partial product. In a first version using the three-input adder, one can decrement the multiplier digit by either one or two while adding the multiplicand to the partial product through the B only or B and C inputs of the three-input adder. In a second version, if the multiplier digit is greater than five, one can add ten times the multiplicand (a left 4 shift in packed decimal) and then subtract by one or two times the multiplicand. The first version requires an average of 2.5 additions per multiplier digit, the second version requires an average of 1.7 additions per multiplier digit. The two- input method referred to above requires an average of 4.5 additions per multiplier digit. Decimal-to-Binary Conversion.

If the decimal numbers are stored in binary-coded decimal (BCD) form, one need only add each BCD digit to the binary number, multiply by ten (in binary) and repeat. This can all be done in one step with the three-input. adder. Multiplying a binary number by ten (1010...