HLASM Language Reference

DC Instruction
ROUTINE B
GAMMA DXD 5D
DELTA DXD 1F
ZETA DXD XL22
.
.
DC
Q(GAMMA)
DC
Q(DELTA)
.
.
ROUTINE C
EPSILON DXD
4H
ZETA DXD 4F
.
.
DC
Q(EPSILON,ZETA)
.
.
Each of the three routines is requesting an amount of work area. Routine A wants
| 2 doublewords and 4 fullwords; Routine B wants 5 doublewords, 10 fullwords, and
| 22 bytes; Routine C wants 4 halfwords and 4 fullwords. During program linking,
| identically named dummy sections are combined, retaining their strictest alignment
| and longest length. For example, Routines B and C both request storage named
| ZETA: the resulting allocation will be 22 bytes on a fullword boundary. When
| program linking is complete, the sum of these individual dummy external section
| lengths is placed in the location of the CXD instruction labeled OMEGA. Routine A
| can then allocate the amount of storage that is specified in the CXD location, and
| each dummy external section's offset within the allocated storage is found in the
| Q-type offset constant referencing its name. Q-type offset constants are described
| at “Offset Constant—Q” on page 159.
DC Instruction
You specify the DC instruction to define the data constants you need for program
execution. The DC instruction causes the assembler to generate the binary
representation of the data constant you specify into a particular location in the
assembled source module; this is done at assembly time.
| Note that the DC instruction's name — Define Constant — is somewhat misleading:
| DC simply creates initial data in an area of the program. The contents of that area
| may be modified during program execution, so the original data isn't truly
| “constant.” If you want to declare values that are more likely to behave like
| constants, use literals (“Literals” on page 40); the assembler attempts to detect and
| diagnose instructions that might change the contents of a field defined by a literal.
If a control section has not been established previously, DC will initiate an unnamed
(private) control section.
The DC instruction can generate the following types of constants:
126 HLASM V1R5 Language Reference