ZX Time #04 17 ноября 2001

Программирование

Discussion - "multitasking OS and on the Spectrum.

Discussion. On multitasking.


                                DJ Blast

 Battle unfolded with unprecedented force
 -------------------------------------

  DJ Blast ^ TNL InSys presents to your
the attention of another batch of my thoughts
on "Axle ZX". As they say, like a discussion - get someone not 
hiding, I do not fault! 


  Unfortunately, the disc ZXT # 3 Visit
aliens, so I will quote in
memory, sorry if where mistaken ...


  Firstly, it is very sad that
many people the word Windows and PC are
virtually synonymous. I sincerely
sorry for those people who are unable to distinguish between 
the platform and OPERATING SYSTEM (please do not

take this phrase as an insult) ... I propose to finish this 
discussion on this issue as irrelevant to the subject ZXTime 
(keyword Still ZX!).



  With regard to IS-DOS, then their experience with it (a 
small, unfortunately ... or can fortunately?) I can conclude 
that the only worthwhile thing in it was just a text editor. In 
addition to work in the IS-Dos, required nerves of steel and 
cast iron drive, and even in this If work is reminiscent of the 
session sadomasochism ... Although it's been so long, maybe 
since the time that something has changed? 


  Go back to the Relocation Tables. The phrase "And if a 
program has a length of 100 K?" looks very funny. I wonder where

did you find such a program? :) Even
in the Black Raven volume of executable code
significantly less. But in any case,
even if it is 100K, then one block of a
program will not be able to download a purely
physically. It is necessary because the page scroll.
Hence the conclusion: keep your beer cold ...
Oops! what am I doing?? Here's a pancake! The conclusion is 
this: any program will still be boot blocks. And you can 
customize each unit separately. In general, those

blocks that will be in the top pages of memory settings is
needed, it is still all the pages begin
from one address.


  The structure of the axis can argue very
long. For example, it is believed that the axis on
Speke should represent only
driver disk (including
screw!) and a new file system. A
Here's a C compiler, the more dynamic, as you suggest, IMHO idea
generally very, very ill-conceived.
This is also a brake will be! Even on PCs
where power is much higher percent, such
Languages ​​do not apply. Any such
language would require the universalization of its operators, 
and higher flexibility, the less speed. As proof:

look at the toy "The Double". She
compiled from some high-level language (I do not know from 
what). Well how? Head is not spinning on the speed? ;)

And when the dynamic compilation will be more
worse. What about "Podvyshennogo level." I
understand, ZXASM_3.10 rulez 4eva (itself named
enjoy:), but there it was only about
macro system, and then only as a
jokes. Here's one I can agree:
need a set of standard procedures and a standard interface with 
them, that is the standard entry point, but that's all! Call 
them from asma will be much more convenient and more clearly 
than from any higher level language. 


  At the end of this round;))) I want to
put forward the idea. Perhaps something like this
already, but I do not know. Discarded ROM
Basic128 (which in itself is not new) and
replace it with a combination of ROM and RAM.
Let me explain: say, to address # 0000 .. # 03FF
will PZUshka with hardwired loader axis
and the remaining addresses (# 0400 .. # 3FFF) - RAM
in which we will ship the core axis of the disk. That would be 
enough, but unfortunately sometimes a clear screen roughly this 
way: 


    ld hl, 23297

    xor a
l1 dec hl

    ld (hl), a

    or (hl)

    jr z, l1

    ...


  For our axis, and it will end very
very sad. Therefore, we must add
port to protect the lower memory of such abuse. It is 
understood that Depending on the state of the port

will enable / disable recording
Address # 0000 .. # 3FFF. Example:

; Some example of OS loader:


    ld bc, port; port address yn
                      ; Poisoning protection

                      ; Memory

    ld a, 1, to allow entry

    out (c), a; without comments


    ld hl, # 0400; \

    ld de, adr_on_disk; \

    ld b, sec_len;} Loading

    ld c, load; /

    call disk_driver; /

    ...

    ld bc, port

    xor a; ban record

    out (c), a

    ...


  All this mess will require revision
iron, but "if nothing is further developed,
what do you can get? "(c) Steel
Drugon. I do not zhelezyachnik, but people in the know
say that such a revision is implemented
simple enough. And if we consider that
most spektrumistov sits on
emulators, you can simply refer to
authors of emulators to support the
this option.


  The advantages of such an axis can be attributed
that each new version does not require
pereshivki ROM, and in general, each user will be able without 
difficulty to patch an axis for their black purposes. Again, 
all system variables can be stored in the body of the axis,

leaving all of main memory program
user. And anyway, you can come up with a lot more applications 
of this memory even if the axis is not necessary ...



  At this until finished. It is interesting to know
The view of readers of my sentence. Until
on the air:)


                 - - -


          Comments from DWT:


  I am happy as a kid:). Still mnogozadchnost, OS, and even 
language pod_vyshennogo level caused a reaction among the 
masses. Mean people are not indifferent to the fate of the 
Spectrum, as a living computer, where in addition to high-tech 
programming, which already seems to be reaching their maximum, 
and develop technology 'Docking' human computer '.



  Dispute about the structure of the OS can
really, really long. Why are we,
in fact, brewed this mess ...


  Note that it is impossible to distinguish between the OS
and ignore the platform. Crimes immediately to the reasoning of 
the high-level language. At some times I say this: Spectrum - 
Zhelezyaki peculiar, so he NEEDS And a peculiar, distinct 
language. Let this language will be structurally similar to the 
assembler and even something to remind you to duplicate. Let it 
be even assembler, a which will be expanded macros ...



  Very pleased that the program of a hundred kilobytes amused 
by our readers. And to He even ripped his stomach with laughter,

admit I was somewhat wrong. I
simply not reflected upon the essence and not figured
volumes relocation tables. Sorry, got excited.


  The idea of ​​replacing part of the RAM already PZU'shkoy
is not new. However, if you implement it really gives a free 
hand and it becomes possible to rivet different OS'y for every 
taste. The idea is very interesting, Why, then, in its 
implementation, each play (say) will have its own

Operating system, tailored to fit its own requirements. Go tell 
DJ Blast'u - one thinker in terms of ideas about ROM + RAM with

you have:).


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