Zortech "limitation"

[Peter Nelson]

 bright at Data-IO.COM (Walter Bright) posts...

><  If I wanted to do pointer arithmetic all over the place I would
><  use Assembler!   Zortech C/C++ is allegedly a high-level language
><  but their manual describes this as a "limitation" of their product.
><  I would call it a bug. 
>
>There's no assembler in the example above. One man's bug is another's feature.
>C is not a high-level language, it's a "portable assembler", thus the
>limitations and capabilities of the underlying instruction set are
>reflected in the source code. I occasionally get "bug" reports that the
>compiler does not make the PC look like a VAX.

   I don't think its the job of the compiler to make one brand of com-
   puter look like another, whether it's a case of a PC looking like
   a VAX or a Mac looking like a Sun.   Rather, it is to make all
   computers look like the same virtual machine, in this case a
   "C" computer.  

   The key word in Mr. Bright's above paragraph is "portable". 
   Languages achieve portability by allowing the programmer to 
   write his code in a way which is not dependent on the architectual
   whims or affectations of a particular hardware vendor.  In order
   to achieve this it is necessary to obscure the underlying features of
   the target machine's architecture.   In principle I ought to be
   able to take a program which I wrote on my HP/Apollo DN10000
   and port it to my PC or my friend's Mac or my wife's DG Aviion just
   by recompiling it.   This is NOT achieved by making the Aviion, PC,
   or Mac look like a DN10000.  

   In practice, of course, mapping C to a particular architecture may
   be much harder in some cases than others.   80x86's certainly 
   offers some challenges to the compiler writer and the programmer
   may sacrifice some performance to have the architecture hidden from
   him, but that should be his choice.   In today's heterogeneous
   environments, portability is becoming increasingly important and
   I may prefer to take a performance hit if it means not having to 
   rewrite my code when I go from an Apollo to a PC. 

                                               ---Peter
                                                                

   
   PS-  A philosophical point:  The average computer has become vastly
        more powerful in recent years.  An XT might be a 0.5 MIPS 
        machine, but 386's are running 5-7 MIPS and '486's are claiming
        10-15 MIPS.   Motorola is claiming 20 MIPS for their 25 MHz
        68040 and say they will have a 50MHz part out in a year.

        In such an environment productivity, ease of maintenance, 
        readability of code and portability of code may outweigh
        the small loss of efficieny suffered by having the compiler
        generate some DS-register manipulations behind the scenes,
        however much a hack this might seem to the compiler-writer.

        Memory and CPU cycles are a LOT cheaper than they used to be 
        and our priorities should reflect this.