Re: Efficiency of code generated by Ada compilers

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Sat, 14 Aug 2010 01:29:56 +0200, <tmoran@acm.org> a écrit:
>   The Burroughs machines were like that.  The descriptor pointing to
> an array included the size as well as the base address, so index in-range
> was automatically checked by the hardware.
So these old machines were in some way safer than ones of nowadays

A similar thing exist with Intel CPUs : memory segment are defined using a  
base and a limit. This may be feasible to assign a memory segment to each  
array and then get the same check done (an hardware exception would be  
raised if ever an attempt to access a byte beyond the limit was maid),  
while this would come with a cost, at least the one to have to switch  
memory segment register all the time (this is more costly than reading and  
writing any other register).

I found a nice page about Burroughs machines and others:
http://www.cs.virginia.edu/brochure/museum.html

Nice historical document

Near the bottom a the page, an photo of a pins labeled “I touched a B5000”  
(which as the page said, was one of these Burroughs machines)


If you go down into the page, there is another picture, of an addressable  
magnetic tape containing the Nicklaus Wirth's Pascal compiler (touching,  
if I may say so)