Ed Jaffe writes: > We use 'Jxx *+2' which disturbs no registers and is guaranteed to fail > with an 0C1.
I like that; OK by assembler and no branch in the normal case but guaranteed to program check on 00. If my old code that uses TRAP ever needs to be updated to a relative addressing version, I will consider using that. I only use this technique for integrity and consistency checks that should never fail in normal execution. If a TRAP triggers it either indicates an internal error situation that should not be possible or a deliberate attempt to use some code in a non-supported way, perhaps in an attempt to bypass checks. Jonathan Scott, HLASM IBM Hursley, UK