Re: S/390 (was Market pressures for more reliable software)

[robin <robin_v@bigpond.nospam.com>]

Roedy Green <roedy@mindprod.com> writes: > On Thu, 28 Jun 2001 11:44:29 GMT, robin <robin_v@bigpond.nospam.com>
> wrote or quoted :
> 
> >With the BALR instruction, one or
> >more registers can be loaded with the absolute address of the next
> >instruction.  This register(s) can then be used as the
> >base register(s).  No address constants needed.
> 
> The BALR was S/360's rather odd subroutine jump instruction.
> 
> BALR 14,15 would put the return address in reg 14 and jump to the
> subroutine addressed by reg 15.

But when the second address is zero, it does not branch, and
the address of the next instruction is placed in the nominated
register.  (e.g., BALR 3,0)

This value (contents) is then used as the base for addressing purposes.

> Roedy Green, Canadian Mind Products
> Custom computer programming since 1963. Ready to take on new work.