Binary to Decimal help...

This is a discussion on Binary to Decimal help... within the C Programming forums, part of the General Programming Boards category; i cant figure out how i should write a c program regarding this problem... when i enter a binary number,say ...

  1. #1
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    Binary to Decimal help...

    i cant figure out how i should write a c program regarding this problem...

    when i enter a binary number,say 101101, the result would be the decimal equivalent of 45...

    it goes like this,

    1 0 1 1 0 1 equals
    32 16 8 4 2 1

    so,form right to left, it goes like 1,2,4,8,16,32,64,128,256,512,1024...so on...(like IP addressing,VLSM...)
    it will add only on values of 1 and not 0...

    counting is from right to left,but it wont start until 1 is the rightmost...

    using if and then or loops is not allowed...only arithmetic operators...

    thanks in advance...

  2. #2
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    just write the program using loops, then remove the loop, and copy the inside of the loop into your code over and over

    edit: if your just learning how to program, im sorry, but you have a terrible teacher/lecturer/tutor/textbook
    Last edited by LordPc; 07-01-2010 at 08:43 AM.

  3. #3
    spurious conceit MK27's Avatar
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    Quote Originally Posted by anarcho View Post
    using if and then or loops is not allowed...only arithmetic operators...
    Without using at least a while() loop, you can only do this if the number is of fixed length, and then it will just be cut and paste some almost identical code over and over. Here's a clue: put the binary number into a char string:
    Code:
    char num[]="101101";
    So the fixed length is 6. If you want to work right to left (aka "big endian"), start with num[5]:
    Code:
    int total = 0, add = 1;
    if (num[5] == '1') total += add;
    add *= 2;
    if (num[4] == '1') total += add;
    add *= 2;
        [...etc]
    If you can't even use "if", those lines could be:
    Code:
    total += add*(num[5] - '0');
    Notice, '0' (which '0' == 48) not 0. For an understanding of that read up on the ASCII table:
    http://www.idevelopment.info/data/Pr...ii_table.shtml
    http://en.wikipedia.org/wiki/ASCII
    Last edited by MK27; 07-01-2010 at 10:23 AM.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  4. #4
    {Jaxom,Imriel,Liam}'s Dad Kennedy's Avatar
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    Is this a recursion problem you are supposed to do? Cause, without using loops, that is about the only way to do it.

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    So why can't you go from left to right? Might be easier IMO.

    [Edit] as noted recursion is the only alternative if loops are a no-no.
    Last edited by itCbitC; 07-01-2010 at 10:57 AM.

  6. #6
    spurious conceit MK27's Avatar
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    Quote Originally Posted by itCbitC View Post
    [Edit] as noted recursion is the only alternative if loops are a no-no.
    No, if this is to deal with a fixed number of bits (in the example, 6), you don't need either, but you will end up with some "worst practice" long noodle style code exemplifying unnecessary duplication.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

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    Would it really be possible to do with recursion without "if" ?

  8. #8
    Registered User claudiu's Avatar
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    Assuming the instructor really wants them to use recursion like Kennedy suggested, then the instructor is an absolute retard. o_O
    1. Get rid of gets(). Never ever ever use it again. Replace it with fgets() and use that instead.
    2. Get rid of void main and replace it with int main(void) and return 0 at the end of the function.
    3. Get rid of conio.h and other antiquated DOS crap headers.
    4. Don't cast the return value of malloc, even if you always always always make sure that stdlib.h is included.

  9. #9
    {Jaxom,Imriel,Liam}'s Dad Kennedy's Avatar
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    Yes. You use return values and tertiaries.

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    Yes but using tertiaries is equivalent to using if statements, what I meant of course is, without any way of testing a condition.

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    Methinks! MK27 has a good point because w/o a fixed no. of input characters this won't be possible w/o using ifs or loops.
    And agree with Susonics too, because even with the use of recursion the EOF condition has to be tested for the input.
    Last edited by itCbitC; 07-01-2010 at 01:23 PM.

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