HLASM Language Reference

DC Instruction—Hexadecimal Floating-Point Constants
Figure 51 (Page 3 of 3). Hexadecimal Floating-Point Constants
Subfield Value Example
Number of values
per operand:
Padding:
Truncation of
assembled value:
Multiple
Correct fraction is
extended to the right and
rounded
Only if rounding mode 5; rounded otherwise.
The format of the constant is shown in Figure 52 on page 165.
The value of the constant is represented by two parts:
An exponent portion (see ▌1▐ in Figure 52 on page 165), followed by
A fractional portion (see ▌2▐ in Figure 52)
A sign bit (see ▌3▐ in Figure 52) indicates whether a positive or negative number
has been specified. The number specified must first be converted into a
hexadecimal fraction before it can be assembled into the correct internal format.
The quantity expressed is the product of the fraction (see ▌4▐ in Figure 52) and the
number 16 raised to a power (see ▌5▐ in Figure 52). Figure 52 shows the
external format of the three types of floating-point constants.
Here is the range of values that can be assembled into hexadecimal floating-point
constants:
Type of
Constant
Range of Magnitude (M) of Values
(Positive and Negative)
E 16−65 ≤ M ≤ (1−16−6) x 1663
D 16−65 ≤ M ≤ (1−16−14) x 1663
L 16−65 ≤ M ≤ (1−16−28) x 1663
E, D, L 5.4 x 10−79 ≤ M ≤ 7.2 x 1075 (approximate)
| If the value specified for a particular constant does not lie within these ranges, the
| assembled value then depends on these factors:
With type extension H, overflows assemble to the largest magnitude for the
| specified type, underflows will denormalize the value or return zero, depending
| on the value and rounding mode.
Without type extension H, certain combinations of exponents (modifier and
| nominal value) may produce invalid results (message ASMA071E), and if the
| exponent is too large it is ignored and the nominal value of the constant
| preceding the exponent is assembled instead.
164 HLASM V1R5 Language Reference