Call parameter lists

AMODE 31 callers of the BPX1xxx service provide a standard 31-bit parameter list. Register 1 contains a 31-bit address that points to a list of 31-bit addresses, which point to the parameters. The last parameter pointer in the list must have the high-order bit set to 1. All storage is below the bar.

AMODE 64 callers of the BPX4xxx service provide a 64-bit address in register 1 that points to a list of 64-bit addresses, which point to the parameters. There is no end-of-parameter list indicator; the high-order bit is part of the 64-bit address. The parameter list and the parameters may or may not exist above the bar.