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# Binary To Decimal Conversion Controls

IP.com Disclosure Number: IPCOM000092576D
Original Publication Date: 1966-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 35K

IBM

## Related People

Prentice, PN: AUTHOR

## Abstract

In the conversion of a fixed point binary number to a binary-coded decimal BCD number, some time can be saved if full use is made of the multiple bit position shifter normally present in large data processing systems. One algorithm generally used for such conversion is to enter the highest binary digit into the units order of a decimal accumulator, double the resulting decimal value, enter the next binary digit into the same position, double the number decimally again, etc. Thus when the last binary digit is entered, the accumulator contains the decimal equivalent of the binary number.

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Binary To Decimal Conversion Controls

In the conversion of a fixed point binary number to a binary-coded decimal BCD number, some time can be saved if full use is made of the multiple bit position shifter normally present in large data processing systems. One algorithm generally used for such conversion is to enter the highest binary digit into the units order of a decimal accumulator, double the resulting decimal value, enter the next binary digit into the same position, double the number decimally again, etc. Thus when the last binary digit is entered, the accumulator contains the decimal equivalent of the binary number.

Binary register 1 retains in true form the magnitude of the binary number to be converted. Since the original binary number includes a sign bit position at the left end, the leftmost digit of the true magnitude must be a 0 for positive signs and can be a 1 for a negative number only if all other digits are 0's. In either case, the leftmost four bits of register 1 contain a valid BCD number.

Register 1 can be outgated to shifter 2 which can shift the output left by one bit position or by four bit positions as determined by shift control 3. On the first cycle of a convert-to-decimal CVD operation, the binary number is shifted left four bit positions. On the other CVD cycles the binary number is left shifted one order with any digits shifted left out of the range of register 1 entered into the rightmost orders of BCD Register 4. Here each group of...