Re: Market pressures for more reliable software

["Shmuel (Seymour J.) Metz" <nospam@acm.org>]

robin wrote:


> No. It used relative addressing, and base-relative addressing.
> (strictly speaking, it used base-displacement-indexed addressing.)
> The assembler allowed "absolute" addresses to be specified,
> which had to be filled in by the loader.

You're confusing two different things. The S/360 used absolute addresses, but they were not present in
instructions. At least, it did until prefixing came along. As to assembler language, it was relocatable addresses
that had to be adjusted by the loader; if the program specified an absolute address, then the loader did not have
to adjust it.

> Any program can be loaded anywhere in memory.
> Programs can be made dynamically relocatable, but only with some effort.

That was the theory in VMS; IBM had to scrap it and replace it with MVS.


> In the days when the 360 first came out, dynamin program relocation
> would have been an advantage (programs were relatively small, say, 200K bytes).
> These days the disadvantage of dynamic relocation is that the
> time taken to relocate a large program 10Mb, 100Mb becomes significant.

No, it's insignificant, because you only need to change the page tables.

--
Shmuel (Seymour J.) Metz