HLASM: V1R6 Language Ref

DC instruction—Hexadecimal floating-point constantsv An exponent portion represented by the excess-64 binary notation, which is thenentered into the characteristic field of the constant.The excess-64 binary notation is obtained by adding +64 to the value of theexponent (which lies between −64 and +63) to yield the characteristic (which liesbetween 0 and 127).Notes:1. The L-type floating-point constant resembles two contiguous D-type constants.The sign of the second doubleword is assumed to be the same as the sign ofthe first.The characteristic for the second doubleword is equal to the characteristic forthe first minus 14 (the number of hexadecimal digits in the fractional portion ofthe first doubleword). No indication is given if the characteristic of the seconddoubleword is zero.The L-type and LH-type floating-point constants are double-word aligned. TheLQ-type is quad-word aligned. A DC 0LQ forces the alignment to a quad-wordboundary.2. If scaling has been specified, hexadecimal zeros are added to the left of thenormalized fraction (causing it to become unnormalized), and the exponent inthe characteristic field is adjusted accordingly. (For further details on scaling,see “Subfield 5: Modifier” on page 134.)3. The fraction is rounded according to the implied or explicit length of theconstant. The resulting number does not differ from the exact value specifiedby more than one in the last place.Note: You can control rounding by using the 'H' type extension and specifyingthe rounding mode.4. Negative fractions are carried in true representation, not in thetwo’s-complement form.5. Duplication is applied after the constant has been assembled.6. An implied length of 4 bytes is assumed for a short (E) constant and 8 bytes fora long (D) constant. An implied length of 16 bytes is assumed for an extended(L) constant. The constant is aligned at the correct word (E) or doubleword (Dand L) boundary if a length is not specified. However, any length up to andincluding 8 bytes (E and D) or 16 bytes (L) can be specified by a lengthmodifier. In this case, no boundary alignment occurs.7. Signed zero values are correctly generated for type extensions H and B.Without a type extension, zero values of either sign are assembled with positivesign.Any of the following statements can be used to specify 46.415 as a positive,fullword, floating-point constant; the last is a machine instruction statement with aliteral operand. Note that each of the last two constants contains an exponentmodifier.DCDCDCDCDCAEE’46.415’E’46415E−3’E’+464.15E−1’E’+.46415E+2’EE2’.46415’6,=EE2’.46415’|The following would generate 3 doubleword floating-point constants.FLOAT DC DE(+4)’+46,−3.729,+473’164 HLASM: V1R6 Language Ref