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Groups > comp.lang.c > #167555
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Beginner....Decimal/Octal converter help |
| Date | 2022-09-08 20:19 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <875yhx65ec.fsf@bsb.me.uk> (permalink) |
| References | <8ffd982c-2e82-4caa-9256-ec17be2efe56n@googlegroups.com> |
ManyBeers <markzuffi@yahoo.com> writes:
> Hello I am teaching myself C and I need some help with a problem.
I think (though I am not sure) that you are also teaching yourself
programming at the same time. That makes it hard. First, because most
of the problems will to do with how you write code -- any code -- but
your be fooled into thinking the problem is you don't know C. Second, C
is a rather fussy language for a beginner to learn. It's small (that's
good) but it is full of odd corners. Third, there are a boat load of
very bad tutorials out there that use C. Don't know why, but the
language seems to attract them.
> After a search for dec/oct convert I found this code:
> (295600127)
> #include <stdio.h>
> #include <math.h>
>
> int convertDecimalToOctal(int decimalNumber);
> int main()
> {
> int decimalNumber;
The number is just a number. It's not decimal and it's not octal. It
may be binary inside the machine, but C lets you treat it like a number.
> printf("Enter a decimal number: ");
This message is OK because you are asking for a number to entered using
decimal digits.
> scanf("%d", &decimalNumber);
Always check that input has been successful. It's one of the most
important habits to get into.
> printf("%d in decimal = %d in octal", decimalNumber, convertDecimalToOctal(decimalNumber));
>
> return 0;
> }
printf can do what you want:
int main(void)
{
int number;
printf("Enter a decimal number: ");
if (scanf("%d", &number) == 1)
printf("%d in decimal = %d in octal = %o\n", number, (unsigned)number);
return 0;
}
And here we hit one of C's corners. The %o format expected an unsigned
int.
> int convertDecimalToOctal(int decimalNumber)
> {
> int octalNumber = 0, i = 1;
>
> while (decimalNumber != 0)
> {
> octalNumber += (decimalNumber % 8) * i;
> decimalNumber /= 8;
> i *= 10;
> }
>
> return octalNumber;
> }
This is weird. Decimal and octal are about representations so one would
expect a function like this generate a string of digits. What this is
doing is computing a number (note neither decimal nor octal, just a
number) that when printed as a decimal, shows the octal digits that
correspond to the original number.
This is a bad idea for all sorts of reasons. I'll go into them if you
want to know, but it's best to forget you ever saw this function!
> As you can see I posted it has limit of 295600127. why is that.
That's one of the problems. The number which, when printed as a
decimal, shows the digits of the original in octal has to be bigger than
than the original.
> but what I really want is could somebody explain exactly what
> the code is doing below the 1st... return 0;.... which I think is the
> int convertDecimaltoOctal(int decimalNumber)function and it's
> implementation.
> I want to fix the program so it will do at least a full 32bitnumber (4294967295)
> So here octalNumber += (decimalNumber % 8) * i;s how I see it: the code defined 2 variables octalnumber=0
> and i=1 then it goes into a whileloop ...while decimalNumber is not 0...
> do this:
> octalNumber += (decimalNumber % 8) * i; modulus the decNum(say 1000) multiply that by i (which equals 1 for now) increment and then assign to
> octNum? The doing something and then assigning is tricky. Anyways if
> you know how could you explain exactly what the function does and in
> which order.
Ditch the whole idea of this function. Decimal and octal are about
representations as strings of digits. If you don't want to use %o, the
function you need should write digits into a string buffer:
void octal_digits(int n, char *buf, size_t len);
You could, of course, return an allocated string, but already you are
hitting C issues that have nothing to do with programming.
> This is my own oct/dec converter:
> /*decimal_octal_converter*/
>
> #include <stdio.h>
> /*---------------*/
>
> unsigned int dec, oct;
>
> int main(void)
>
> {
> printf("Enter a number between 0 and 4294967295: ");
> scanf ("%d", &dec);
>
>
> printf("Octal value: %d%d%d%d%d%d%d%d%d%d%d",
> dec/(8*8*8*8*8*8*8*8*8*8),
> dec%(8*8*8*8*8*8*8*8*8*8)/(8*8*8*8*8*8*8*8*8),
> dec%(8*8*8*8*8*8*8*8*8)/(8*8*8*8*8*8*8*8),
> dec%(8*8*8*8*8*8*8*8)/(8*8*8*8*8*8*8),
> dec%(8*8*8*8*8*8*8)/(8*8*8*8*8*8),
> dec%(8*8*8*8*8*8)/(8*8*8*8*8),
> dec%(8*8*8*8*8)/(8*8*8*8),
> dec%(8*8*8*8)/(8*8*8),
> dec%(8*8*8)/(8*8),
> dec%(8*8*8)%(8*8)/8, dec%8);
>
> return 0;
> }
> it is the only way I could figure out how to do it.
You need exercises to learn about recursive functions and/or loops.
What resources are you using to learn?
--
Ben.
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Beginner....Decimal/Octal converter help ManyBeers <markzuffi@yahoo.com> - 2022-09-08 11:34 -0700
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-08 11:56 -0700
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-08 20:19 +0100
Re: Beginner....Decimal/Octal converter help Barry Schwarz <schwarzb@delq.com> - 2022-09-08 12:34 -0700
Re: Beginner....Decimal/Octal converter help Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2022-09-08 20:38 -0600
Re: Beginner....Decimal/Octal converter help Öö Tiib <ootiib@hot.ee> - 2022-09-09 03:22 -0700
Re: Beginner....Decimal/Octal converter help gazelle@shell.xmission.com (Kenny McCormack) - 2022-09-09 13:30 +0000
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-09 09:16 -0700
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-09 19:06 +0000
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-10 11:58 +0200
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-10 11:37 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-10 13:05 +0200
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-10 14:42 +0000
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-10 16:10 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-10 18:14 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-10 12:54 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-10 16:22 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-10 19:03 +0100
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-10 19:30 +0100
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-10 19:47 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-11 14:07 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-11 16:12 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-11 17:58 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-11 21:14 +0100
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-11 20:01 -0700
Re: Beginner....Decimal/Octal converter help Richard Damon <Richard@Damon-Family.org> - 2022-09-11 23:32 -0400
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-12 13:52 +0000
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-14 03:24 -0700
Re: Beginner....Decimal/Octal converter help Richard Damon <Richard@Damon-Family.org> - 2022-09-14 08:10 -0400
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-12-26 06:09 -0800
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-12 16:53 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-12 16:48 +0100
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-12 17:46 +0100
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-12 20:37 +0100
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-13 00:03 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-13 12:31 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-13 12:48 +0100
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-13 14:18 +0100
Re: Beginner....Decimal/Octal converter help Anton Shepelev <anton.txt@g{oogle}mail.com> - 2022-09-13 17:13 +0300
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-13 16:50 +0100
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-13 18:47 +0100
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-14 03:16 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-13 20:15 +0200
Re: Beginner....Decimal/Octal converter help Kaz Kylheku <480-992-1380@kylheku.com> - 2022-09-13 20:29 +0000
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-13 22:22 +0100
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-13 14:37 -0700
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-13 23:16 +0100
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-13 22:16 +0000
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-13 16:15 -0700
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-13 16:15 -0700
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-14 10:58 +0100
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-14 15:36 +0100
Re: Beginner....Decimal/Octal converter help Richard Harnden <richard.nospam@gmail.com> - 2022-09-14 21:53 +0100
Re: Beginner....Decimal/Octal converter help Kaz Kylheku <480-992-1380@kylheku.com> - 2022-09-14 05:55 +0000
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-14 10:10 +0200
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-14 07:54 -0700
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-14 18:32 +0200
Re: Beginner....Decimal/Octal converter help Bart <bc@freeuk.com> - 2022-09-14 18:39 +0100
Re: Beginner....Decimal/Octal converter help Kaz Kylheku <480-992-1380@kylheku.com> - 2022-09-15 01:12 +0000
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-15 09:11 +0200
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-15 08:07 -0700
Re: Beginner....Decimal/Octal converter help Kaz Kylheku <480-992-1380@kylheku.com> - 2022-09-14 18:40 +0000
Re: Beginner....Decimal/Octal converter help Kaz Kylheku <480-992-1380@kylheku.com> - 2022-09-14 05:45 +0000
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-14 12:11 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-14 09:57 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-14 03:09 +0100
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-14 10:29 +0200
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-14 15:14 +0100
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-14 07:36 -0700
Re: Beginner....Decimal/Octal converter help Öö Tiib <ootiib@hot.ee> - 2022-10-03 01:10 -0700
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-10-03 11:36 +0100
Re: Beginner....Decimal/Octal converter help Öö Tiib <ootiib@hot.ee> - 2022-10-04 02:13 -0700
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-10-04 16:27 +0100
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-13 11:48 -0700
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-14 10:38 +0200
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-14 14:27 +0000
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-14 07:58 -0700
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-16 13:06 -0700
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-16 13:16 -0700
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-12 17:55 +0000
Re: Beginner....Decimal/Octal converter help Kaz Kylheku <480-992-1380@kylheku.com> - 2022-09-12 18:22 +0000
Re: Beginner....Decimal/Octal converter help Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-09-12 20:41 +0100
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-11 15:45 -0700
Re: Beginner....Decimal/Octal converter help Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-09-11 15:41 -0700
Re: Beginner....Decimal/Octal converter help David Brown <david.brown@hesbynett.no> - 2022-09-12 17:06 +0200
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-11 06:46 -0700
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-11 06:57 -0700
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-11 07:07 -0700
Neologism (Was: Beginner....Decimal/Octal converter help) gazelle@shell.xmission.com (Kenny McCormack) - 2022-09-11 14:18 +0000
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-11 16:33 +0000
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-13 15:40 -0700
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-09 23:08 +0000
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-11 06:37 -0700
Re: Beginner....Decimal/Octal converter help scott@slp53.sl.home (Scott Lurndal) - 2022-09-11 16:31 +0000
Re: Beginner....Decimal/Octal converter help Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-09-13 15:44 -0700
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