HLASM Language Reference

DC Instruction—Fixed-Point Constants
Range of values that can
Length be assembled
8 −263 to 263−1
4 −231 to 231−1
2 −215 to 215−1
1 −2 to 2−1
The range of values depends on the implicitly or explicitly specified length (if
scaling is disregarded). If the value specified for a particular constant does not lie
within the allowable range for a given length, the constant is not assembled, but
flagged as an error.
A fixed-point constant is assembled as follows:
1. The specified number, multiplied by any exponents, is converted to a binary
number.
2. Scaling is done, if specified. If a scale modifier is not provided, the fractional
portion of the number is lost.
3. The binary value is rounded, if necessary. The resulting number does not differ
from the exact number specified by more than one in the least significant bit
position at the right.
4. A negative number is carried in two's-complement form.
5. Duplication is applied after the constant has been assembled.
The statement below generates 3 fullwords of data. The location attribute of CONWRD
is the address of the first byte of the first word, and the length attribute is 4, the
implied length for a fullword fixed-point constant. The expression CONWRD+4 could
be used to address the second constant (second word) in the field.
CONWRD DC 3F'658474'
Figure 42 (Page 1 of 2). Fixed-Point Constants
Subfield Value Example Result
1. Duplication factor Allowed
2. Type F and H
3. Type Extension D permitted with
type F
| 4. Program type Allowed
5. Modifiers
Implicit length:
(length modifier
not present)
Alignment:
(Length modifier
not present)
Doubleword: 8 bytes
Fullword: 4 bytes
Halfword: 2 bytes
Doubleword,
fullword or
halfword
Range for length: 1 to 8
(byte length)
.1 to .64
(bit length)
Chapter 5. Assembler Instruction Statements 149