HLASM Language Reference

DC Instruction—Hexadecimal Floating-Point Constants
The excess-64 binary notation is obtained by adding +64 to the value of the
exponent (which lies between −64 and +63) to yield the characteristic (which lies
between 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 of
the first.
The characteristic for the second doubleword is equal to the characteristic for
the first minus 14 (the number of hexadecimal digits in the fractional portion of
the first doubleword). No indication is given if the characteristic of the second
doubleword is zero.
| The L-type and LH-type floating-point constants are double-word aligned. The
| LQ-type is quad-word aligned. A DC LQ forces the alignment to a quad-word
| boundary.
2. If scaling has been specified, hexadecimal zeros are added to the left of the
normalized fraction (causing it to become unnormalized), and the exponent in
the characteristic field is adjusted accordingly. (For further details on scaling,
see “Subfield 5: Modifier” on page 136.)
3. The fraction is rounded according to the implied or explicit length of the
constant. The resulting number does not differ from the exact value specified
by more than one in the last place.
Note: You can control rounding by using the 'H' type extension and
specifying the rounding mode.
4. Negative fractions are carried in true representation, not in the
two'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 for
a 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 (D
and L) boundary if a length is not specified. However, any length up to and
including 8 bytes (E and D) or 16 bytes (L) can be specified by a length
modifier. 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 positive
sign.
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 a
literal operand. Note that each of the last two constants contains an exponent
modifier.
DC
E'46.415'
DC
E'46415E–3'
DC
E'+464.15E–1'
DC
E'+.46415E+2'
DC
EE2'.46415'
AE
6,=EE2'.46415'
The following would generate 3 doubleword floating-point constants.
166 HLASM V1R5 Language Reference