HLASM Language Reference

Terms, Literals, and Expressions
The following example shows how to use the length attribute to move a character
constant into either the high-order or low-order end of a storage field.
A1 DS CL8
B2 DC CL2'AB'
HIORD MVC A1(L'B2),B2
LOORD MVC A1+L'A1-L'B2(L'B2),B2
A1 names a storage field 8 bytes in length and is assigned a length attribute of 8.
B2 names a character constant 2 bytes in length and is assigned a length attribute
of 2. The statement named HIORD moves the contents of B2 into the first 2 bytes of
A1. The term L'B2 in parentheses provides the length specification required by the
instruction.
The statement named LOORD moves the contents of B2 into the rightmost 2 bytes of
A1. The combination of terms A1+L'A1-L'B2 adds the length of A1 to the beginning
address of A1, and subtracts the length of B2 from this value. The result is the
address of the seventh byte in field A1. The constant represented by B2 is moved
into A1 starting at this address. L'B2 in parentheses provides the length
specification in both instructions.
For ease in following the preceding example, the length attributes of A1 and B2 are
specified explicitly in the DS and DC statements that define them. However, keep
in mind that the L'symbol term makes coding such as this possible in situations
where lengths are unknown. For example:
C3 DC C'This is too long a string to be worth counting'
STRING MVC BUF(L'C3),C3
Other Attribute References
Other attributes describe the characteristics and structure of the data you define in
a program; for example, the kind of constant you specify or the number of
characters you need to represent a value. These other attributes are:
Count (K')
Defined (D')
Integer (I')
Number (N')
Operation code (O')
Scale (S')
| Type (T'); allowed only in conditional assembly.
You can refer to the count (K'), defined (D'), number (N'), and operation code
(O') attributes only in conditional assembly instructions and expressions. For full
details, see “Data Attributes” on page 324.
Literals
You can use literals as operands in order to introduce data into your program. The
literal is a special type of relocatable term. It behaves like a symbol in that it
represents data. However, it is a special kind of term because it also is used to
define the constant specified by the literal. This is convenient because:
The data you enter as numbers for computation, addresses, or messages to be
printed is visible in the instruction in which the literal appears.
You avoid the added effort of defining constants elsewhere in your source
module and then using their symbolic names in machine instruction operands.
40 HLASM V1R5 Language Reference