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decimal numbers
summary
Decimal numbers are typically represented as binary coded decimals (BCDs), other than on some early decimal computers (and even often then).
The basic pattern is to store the decimal digits zero (0) to nine (9) in four binary bits. The extra binary combinations possible with four bits (decimal numbers 10, 11, 12, 13, 14, and 15 -or- hexadecimal numbers A, B, C, D, E, and F) are not used. The next higher order decimal digit is stored in the next higher order four binary bits.
Many CISC-style computers include BCD as a hardware supported data type, although usually with only a limited number of arithmetic operations.
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decimal numbers
Decimal numbers are typically represented as binary coded decimals (BCDs), other than on some early decimal computers (and even often then).
The basic pattern is to store the decimal digits zero (0) to nine (9) in four binary bits. The extra binary combinations possible with four bits (decimal numbers 10, 11, 12, 13, 14, and 15 -or- hexadecimal numbers A, B, C, D, E, and F) are not used. The next higher order decimal digit is stored in the next higher order four binary bits.
Many CISC-style computers include BCD as a hardware supported data type, although usually with only a limited number of arithmetic operations.
C does not have a decimal format.
Fixed Decimal declarations:
type of data: coded arithmetic (Binary Coded Decimal, packed two decimal digits to a single 8-bit byte)
S/360, S/370 data format: packed decimal
default precision: five (5) decimal digits
maximum precision: 15 decimal digits
example:
DECLARE DOLLAR_AMOUNT FIXED DECIMAL (9,2) INIT (100.00);
May be declared as FIXED, FIXED DECIMAL, or DECIMAL FIXED.
First number in declaration is the total number of stored digits. Second number in declaration (optional) is the number of digits to the right of an implied decimal point. If the second number is zero or left out, then the number is an integer.
Fixed decimal is more efficient if the precision is declared as an odd number of digits (because of extra code generated to guarantee that the last half of an even number of decimal digits remains zero). Numbers too large to fit into the specified storage will be truncated. Numbers too small to fill the entire storage space will be zero-filled.
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