Invoking the HLASM Services Interface

Use the following steps to invoke a service:

General Purpose Register 1 must point to the HLASM Services Interface block.
Set the service request type, the number of argument words, and the argument words in the HLASM Services Interface block, as described for the service you are requesting.
General Purpose Register 15 is the entry point to all HLASM Services Interface services. Its address is placed in the HLASM Services Interface block by HLASM. The AMODE (high order) bit set on the service entry-point address in the HLASM Services Interface Block.
General Purpose Register 14 contains the return address to the service requester. The assembler resets the caller's AMODE mode back to what was provided at entry.
All registers are restored by HLASM on return.

The supported services and their service-interface descriptions are shown below.