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Re: Learning ARM machine code

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In article <5c878d77feNews04@avisoft.f9.co.uk>,
   Martin <News04@avisoft.f9.co.uk> wrote:
> In article <5c87850775bavariasound@chiemgau-net.de>,
>    Alexander Ausserstorfer <bavariasound@chiemgau-net.de> wrote:
>>In article <5c87163b82News04@avisoft.f9.co.uk>,
>>   Martin <News04@avisoft.f9.co.uk> wrote:
>>> In article <5c87099f9bbavariasound@chiemgau-net.de>,
>>>    Alexander Ausserstorfer <bavariasound@chiemgau-net.de> wrote:
>>>> However, you can do this much easier. Just write the hex
>>>> values

>>> > 01 00 00 EF 48 61 72 72 69 65 74 00 0E F0 A0 E1

>>> That to my mind is MUCH harder, and would give you maintenance
>>> nightmares, as it is impossible to read easily. The computer is
>>> MUCH better translating plain text into hex and binary then we
>>> are.

>>> I strongly suggest that is not the way to program these days. It
>>> was bad enough 50 years ago, when that was the only option, but
>>> certainly not now.

>> I don't understand that. The values are much more clear to me.
>> Without I couldn't understand how computers are working.

> Good luck in understanding it in a year ... or two ...or many more.
> Hex code I would not even try, stopping and improvment or development.

> As Steve said, we may have to agree to differ!

May it be. For me, machine code is much more easy to understand. Because
you don't need a compiler it means that there is nothing between you and
the machine.

You have to know something like a command of ARM (here 32 bit) is 32 bit
wide (or 4 bytes what means 8 places in hex). The command beginns with
the most significant byte why all four bytes has to be read reversed in
byte oder. This makes thinks a bit more complicate because in memory you
start with byte four and go back to byte one for each command.

The example was:

EF000001 72726148 00746569 E1A0F0E0

In memory this is written in byte order, however:

(Order counted here in decimal):

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

01 00 00 EF 48 61 72 72 69 65  74  00   0E  F0  A0  E1

EF is the command for jumping to a routine of the OS. You're calling
this SWI. Learning SWI or EF doesn't matter. Both sais nothing so you
have to learn and to know in any way what it means.

000001 is the number of the routine (or SWI). EF is shorter as SWI and
1 is much shorter as this long string "OS_WriteS". With the number, you
will get more easy the idea of the table of routines EF links to.

When you read the Programmers Reference Manuals about subroutine 1
(or OS_WriteS) you'll learn that this routine uses the next bytes to
print them as ASCII characters on the screen. The bytes have to be ASCII
encoded and the routine ends by zero, so the bytes 5 up to 11 have to be
interpreted as ASCII code.

5. 48 = "H"

6. 61 = "a"

7. 72 = "r"

8. 72 = "r"

9. 69 = "i"

10. 65 = "e"

11. 74 = "t"

Byte 12. has the value 00. It stops the subroutine 1.

E1 A0 F0 0E writes the value from register &E (LR or fourteen) back to
register &F (PC or fiveteen) what means that it gives the controll back
to the OS. Because &F is the Programm Counter. It says to the CPU which
command from which position in memory it should take next.

We had one and a half year of programming C in the school but this way
we learnt nothing. It is too abstract. You won't understand how
computers are working and you don't understand what you are doing.
Everything is hidden before you. You are stuck to the compilers. This is
why I started learning ARM machine code.

A.

-- 
http://home.chiemgau-net.de/ausserstorfer/

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Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-04-12 15:11 +0200
  Re: Learning ARM machine code Harriet Bazley <harriet@bazleyfamily.co.uk> - 2025-04-13 18:27 +0100
    Re: Learning ARM machine code Jean-Michel <jmc.bruck@orange.fr> - 2025-04-14 11:40 +0200
  Re: Learning ARM machine code Theo <theom+news@chiark.greenend.org.uk> - 2025-04-14 17:56 +0100
    Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-06-07 17:08 +0200
      Re: Learning ARM machine code Sebastian Barthel <naitsabes@freenet.de> - 2025-06-09 13:04 +0000
        Re: Learning ARM machine code Theo <theom+news@chiark.greenend.org.uk> - 2025-06-09 17:36 +0100
          Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-06-10 18:11 +0200
            Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-06-14 17:58 +0200
              Re: Learning ARM machine code Martin <News03@avisoft.f9.co.uk> - 2025-06-14 17:54 +0100
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-06-19 06:31 +0200
                Re: Learning ARM machine code Martin <News03@avisoft.f9.co.uk> - 2025-06-19 10:09 +0100
                Re: Learning ARM machine code Jean-Michel <jmc.bruck@orange.fr> - 2025-06-19 11:32 +0200
              Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-11-02 16:42 +0200
                Re: Learning ARM machine code Martin <News03@avisoft.f9.co.uk> - 2025-11-02 17:01 +0000
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-11-15 14:55 +0200
                Re: Learning ARM machine code druck <news@druck.org.uk> - 2025-11-17 19:08 +0000
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-11-15 15:11 +0200
                Re: Learning ARM machine code Harriet Bazley <harriet@bazleyfamily.co.uk> - 2025-11-15 19:46 +0000
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-12-06 17:57 +0200
                Re: Learning ARM machine code Martin <News04@avisoft.f9.co.uk> - 2025-12-06 18:15 +0000
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-12-07 16:25 +0200
                Re: Learning ARM machine code Martin <News04@avisoft.f9.co.uk> - 2025-12-07 15:57 +0000
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-12-21 17:13 +0200
                Re: Learning ARM machine code druck <news@druck.org.uk> - 2025-12-22 20:02 +0000
                Re: Learning ARM machine code Paul Sprangers <Paul@sprie.nl> - 2025-12-22 23:32 +0100
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2026-01-06 14:42 +0200
                Re: Learning ARM machine code anonymouse <na@ignoreme.com> - 2026-01-06 15:02 +0000
                Re: Learning ARM machine code Jean-Michel <jmc.bruck@orange.fr> - 2025-12-08 10:23 +0100
                Re: Learning ARM machine code Harriet Bazley <harriet@bazleyfamily.co.uk> - 2025-12-06 20:06 +0000
                Re: Learning ARM machine code druck <news@druck.org.uk> - 2025-12-09 08:21 +0000
                Re: Learning ARM machine code Martin <News04@avisoft.f9.co.uk> - 2025-12-09 09:48 +0000
                Re: Learning ARM machine code Richard Ashbery <basura@invalid.addr.uk> - 2025-12-09 10:54 +0000
                Re: Learning ARM machine code Steve Fryatt <news@stevefryatt.org.uk> - 2025-11-15 23:46 +0000
                Re: Learning ARM machine code Theo <theom+news@chiark.greenend.org.uk> - 2025-11-16 11:59 +0000
                Re: Learning ARM machine code Alexander Ausserstorfer <bavariasound@chiemgau-net.de> - 2025-12-06 18:10 +0200
                Re: Learning ARM machine code Steve Fryatt <news@stevefryatt.org.uk> - 2025-12-07 12:18 +0000
          Re: Learning ARM machine code Sebastian Barthel <naitsabes@freenet.de> - 2025-06-10 18:37 +0000

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