Re: [PIC] Learning C

The only book I had access to when I started using C was the K&R C book 
(before ANSI). I remember the section on pointers was a little confusing.

The fact that you know other programming languages (especially assembler) 
is greatly in your favour. Rather than trying to follow a step by step 
tutorial I would suggest you try writing some code in PASCAL then use the 
K&R C book as a reference to convert your PASCAL code to C. You know what 
a loop, conditional statement, function etc is in PASCAL. Use the book to 
find the C equivalents. Just grab the "hello world" program and use it to 
invoke your C translation. You can easily trace through it with a debugger 
(such GDB) to see if it's doing what you think it is. Honestly, I think 
this is the fastest way you'll get into it.

I would personally suggest GCC and GDB on Linux.

Friendly Regards
Sergio Masci

On Mon, 11 Nov 2024, David C Brown wrote:

> I must stress that I want to learn C as a desktop language before
> converting to PIC use..
> Recommendations for a good book would be appreciated
> __________________________________________
> David C Brown
> 43 Bings Road
> Whaley Bridge
> High Peak                           Phone: 01663 733236
> Derbyshire                eMail: [email protected]
> SK23 7ND          web: www.bings-knowle.co.uk/dcb
> <http://www.jb.man.ac.uk/~dcb>
>
>
>
> *Sent from my etch-a-sketch*
>
>
> On Mon, 11 Nov 2024 at 00:26, Isaac Marino Bavaresco <
> [email protected]> wrote:
>
>> I rarely use other people's code, unless it is deemed to be of very high
>> quality. I prefer to study the code and write my own version based on
>> it. It is slow but has proven to save a lot of problems in the long run.
>>
>> I write the absolute majority of my code in C (C99 if possible) and try
>> to keep with GCC. If a platform doesn't have a GCC port it is very
>> likely that I won't adopt it. That's not the case for PICs, which I use
>> for so many years that it predates the GCC wide availability.
>>
>> My LCD routines were written in C in the early 1990s for 8051 MCUs and I
>> still use them for ARM and MIPS (PIC32). If they were written in
>> assembly language I would have needed to recreate them at least five
>> times (AVR, PIC, PIC18F, PIC32, ARM).
>>
>> I rewrote a large part of FATFS, because the code was so complicated and
>> obscure that I could not understand it. I think that I found a few
>> mistakes in the implementation during the process.
>>
>> I also wrote my own RTOS because I was not satisfied with the code of
>> FreeRTOS.
>>
>>
>> Cheers,
>>
>> Isaac
>>
>>
>> Em 10/11/2024 21:36, smplx escreveu:
>> > Hi Isaac,
>> > The point isn't really what I could or should do, it's more to do with
>> > what someone else has written and the rest of us have to use. How
>> > often have you come across some code that was abandoned by the
>> > original author many years ago and has been hacked by uncareing
>> > individuals to fix an immediate problem. How often have you come
>> > across comments that no longer reflect what the code actually does.
>> >
>> > And to make the NaN situation even more interesting a floating point
>> > library might implement NaNs correctly (or not) where the "noddy" MCU
>> > compiler doesn't. This is another reason why it's best to learn C in a
>> > proven high quality dev environment like a PC. Look at the early PIC C
>> > compilers - I dare you not to laugh.
>> >
>> > Another way to express a NaN's character is to say "it is unordered".
>> >
>> > Friendly Regards
>> > Sergio Masci
>> >
>> > On Sun, 10 Nov 2024, Isaac Marino Bavaresco wrote:
>> >
>> >> But you could use also the function 'isnan', which is easier to
>> >> understand for someone reading your code.
>> >>
>> >> There are also other functions like 'isinf', etc.
>> >>
>> >>
>> >> Interestingly, a NaN is not greater, nor smaller nor equal to
>> >> anything, not even itself. It is only different than everything.
>> >>
>> >>
>> >> Cheers,
>> >>
>> >> Isaac
>> >>
>> >>
>> >> Em 10/11/2024 20:09, smplx escreveu:
>> >>> Hi Colin,
>> >>>
>> >>> You might be intested to know that to check for floating point
>> >>> errors / exceptions in C you would use:
>> >>>
>> >>> if (x == x)...
>> >>> or
>> >>> if (x != x)...
>> >>>
>> >>> where x is a float
>> >>>
>> >>> e.g.
>> >>>     float    x
>> >>>
>> >>>     x = 1.0 / 0.0;
>> >>>
>> >>>     if (x != x)
>> >>>     {    // x is a NaN which is an error
>> >>>     }
>> >>>
>> >>> Here clearly "x 'is the same as' x" but the test is "x 'is a NaN'".
>> >>>
>> >>> Friendly Regards
>> >>> Sergio
>> >>>
>> >>> On Sun, 10 Nov 2024, CDB wrote:
>> >>>
>> >>>> I have always separated the difference of =  and == in C by
>> >>>> referring to the latter as 'is the same as'
>> >>>>
>> >>>> if (X is the same as Y) then ......  if (X == Y) then
>> >>>> x = y       x now contains the value of Y.
>> >>>>
>> >>>> Colin
>> >>>>
>> >>>>
>> >>>> --
>> >>>>
>> >>>> [email protected]  11 November 2024
>> >>>>
>> >>>> Hosted by: www.superdomains.com.au
>> >>>>
>> >>>> This email is to be considered private if addressed to a named
>> >>>> individual or Personnel Department, and public if addressed to a
>> >>>> blog,  forum or news article.
>> >>>>
>> >>>>
>> >>>>
>> >>>> __________________________________
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>> >>>>
>> >>>>
>> >>>> On 11/11/2024 08:24:15, "smplx" <[email protected]> wrote:
>> >>>>
>> >>>>>
>> >>>>>
>> >>>>> On Sun, 10 Nov 2024, Neil wrote:
>> >>>>>
>> >>>>>> Agree with a couple things from other comments such as C being
>> >>>>>> high-level assembler and using a PC at first (you can just use
>> >>>>>> gcc already on Linux).
>> >>>>>>
>> >>>>>> Already knowing a structured language is very helpful.
>> >>>>>> But IMO you'll have to wrap your head around pointers, which can
>> >>>>>> get confusing. I find this C visualizer very helpful for figuring
>> >>>>>> out some algorithm... https://pythontutor.com/c.html
>> >>>>>>
>> >>>>>> One more note: = != ==
>> >>>>>> Or in other words, the equal sign ( = ) and the double equal size
>> >>>>>> ( == ) are very different things in C. The first assigns a value
>> >>>>>> and the other compares values. But people new to C will
>> >>>>>> invariably use a single equal for a comparison and the code is
>> >>>>>> true every time, as C will compile it as valid code, do the
>> >>>>>> assignment, then the comparison. You have been warned ;P
>> >>>>>
>> >>>>> Sorry to wade in here but:
>> >>>>>
>> >>>>> if (y = x)...
>> >>>>>
>> >>>>> assigns x to y then compares the result to 0. 0 is nomally taken to
>> >>>>> mean false and "not 0" as true. So it is almost alway true except
>> >>>>> in the case where x is 0.
>> >>>>>
>> >>>>> I'm not sure what happens if x and y are floats and x is a NaN or
>> >>>>> if x and y are structures.
>> >>>>>
>> >>>>> if you're looking for a real headache try debugging a program that
>> >>>>> contains:
>> >>>>>
>> >>>>> if (! x == y)...
>> >>>>>
>> >>>>> Trying to learn C on bare metal is like trying to learn to fly by
>> >>>>> crashing a lot. It's a lot quicker and easier if you learn on a
>> >>>>> simulator.
>> >>>>>
>> >>>>> Friendly Regards
>> >>>>> Sergio Masci
>> >>>>>
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