Callers must also use the following linkage conventions:

• Register 1 must contain the address of a parameter list that is a list of consecutive words, each containing the address of a parameter to be passed. The last word in this list must have a 1 in the high-order (sign) bit.
• Register 13 must contain the address of an 18-word save area.
• Register 14 must contain the return address.
• Register 15 must contain the entry point address of the service being called.
• If the caller is running in AR ASC mode, access registers 1, 13, 14, and 15 must all be set to zero.

On return from the service, general and access registers 2 through 14 are restored (registers 0, 1 and 15 are not restored).