HLASM Language Reference

DROP Instruction
DROP Instruction
The DROP instruction ends the domain of a USING instruction. This:
Frees base registers previously assigned by the USING instruction for other
programming purposes
Ensures that the assembler uses the base register you want in a particular
coding situation, for example, when two USING ranges overlap or coincide
If a control section has not been established, DROP will initiate an unnamed
(private) control section
►►──┬─────────────────┬──DROP──┬─────────────────────┬─────────────►◄
└─sequence_symbol─┘
│ ┌─,───────────────┐
│
└── ▼ ┬─base_register─┬┴─┘
└─label─────────┘
sequence_symbol
is a sequence symbol.
base_register
is an absolute expression whose value represents one of the general registers
0 through 15. The expression in base_register indicates a general register,
previously specified in the operand of an ordinary USING statement, that is no
longer to be used for base addressing.
label
is one of the following:
An ordinary symbol
A variable symbol that has been assigned a character string with a value
that is valid for an ordinary symbol
The ordinary symbol denoted by label must be a symbol previously used in the
name field of a labeled USING statement or a labeled dependent USING
statement.
If neither base_register nor label is specified in the operand of a DROP instruction,
all active base registers assigned by ordinary, labeled, and labeled dependent
USING instructions are dropped.
After a DROP instruction:
The assembler does not use the register or registers specified in the DROP
instruction as base registers. A register made unavailable as a base register
by a DROP instruction can be reassigned as a base register by a subsequent
USING instruction.
The label or labels specified in the DROP instruction are no longer available as
symbol qualifiers. A label made unavailable as a symbol qualifier by a DROP
instruction can be reassigned as a symbol qualifier by a subsequent labeled
USING instruction.
The following statements, for example, stop the assembler using registers 7 and 11
as base registers, and the label FIRST as a symbol qualifier:
172 HLASM V1R5 Language Reference