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 initiates an unnamed (private) control section


>>-+-----------------+--DROP--+-----------------------+--------><
   '-sequence_symbol-'        | .-,-----------------. |   
                              | V                   | |   
                              '---+-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 base_register or label are not 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:

         DROP            7,11
         DROP            FIRST