Thread: [BEGINNER] Binary To Decimal Converter Help

Hello guys,
I was coding a binary to decimal converter but it doesn't work. I tried to find the bug but failed. The problem is: It works fine for numbers like 111 (7) but when I put other binary numbers it gives me wrong answers like 1011 should be 13 but it gives me 15. I feel that problem must be somewhere in line 19. Please help.

Code:

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main()
{
    int bin[100]={0},x,i=0,sum=0,n;
    printf("Lenght of binary number is: ");
    scanf("%d",&n);
    
    printf("What is the binary number, enter ONE DIGIT AT A TIME: ");
    for(x=0;x<n;x++)
    {
        bin[x]=scanf("%d", &bin);
    }


    for(x=0;x<n;x++)
    {
        sum=sum+bin[x]*pow(2,i);
        i++;
    }

    printf("The Number in decimal is : %d",sum);
    return(0);
}

Code:

#include<stdio.h>
#include<conio.h>
#include<math.h>
void main()
{
    int rem,i=0,dec=0;
    long int bin;
    clrscr();


    printf("Enter the binary value\n");
    scanf("%ld",&bin);
    while(bin>0)
    {
        rem=bin%10;
        bin=bin/10;
        dec=dec+(rem*pow(2,i));
        i++;
    }
    printf("corresponding decimal value = %d",dec);
    getch();
}

Originally Posted by stahta01

EDIT: Sorry, it looks like you posted code is correct.
I suggest verify the code be ran matches it.

You are doing nothing to handle case of binary zero.


Edit2: What do you think this line does?

Code:

bin[x]=scanf("%d", &bin);

Code:

warning: format '%d' expects argument of type 'int *', but argument 2 has type 'int (*)[100]' [-Wformat]

I suggest getting a compiler/IDE that gives you warnings!

Edit3: The thing you likely wanted to do.

Code:

scanf("%d", &bin[x]);

Tim S.

Now I changed the &bin to &bin[x]. But it still doesn't work

Code:

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int main()
{
    int bin[100],x,i=0,sum,n;
    printf("Lenght of binary number is: ");
    scanf("%d",&n);

    printf("What is the binary number, enter ONE DIGIT AT A TIME: \n");
    for(x=0;x<n;x++)
    {
        bin[x]=scanf("%d", &bin[x]);
    }


    for(x=0;x<n;x++)
    {
        sum=sum+bin[x]*pow(2,i);
        i++;
    }

    printf("The Number in decimal is : %d",sum);
    return(0);
}

For starters, "sum" isn't initialized before it's used (though it was in the first version you posted).

Originally Posted by Matticus

For starters, "sum" isn't initialized before it's used (though it was in the first version you posted).

It didn't work then either.

Originally Posted by Matticus

Let's look at your original problem and see if we can find some clues.



You say it "works fine for numbers like 111 (7)", but what about another three-bit number?

Binary 101 (5) also produces 7. In fact, any three bit number seems to produce 7. What is 7 in binary? It is 111.

Any four bit number seems to always produce 15. What is 15 in binary? 1111.

Now we've identified a pattern. It seems your code is always behaving as if the input was all ones.

So let's put a print statement in your second "for()" loop to print out the value of "bin[x]" to see what values it holds.

Well! All the elements seem to be one, regardless of what we entered! So maybe the problem isn't with line 19 after all. Let's check out the input on line 13.

Code:

bin[x]=scanf("%d", &bin[x]);

This looks suspicious. Normally when we use "scanf()" to read in an integer, it would look like this:

Code:

scanf("%d", &bin[x]);

The "&binx[x]" tells "scanf()" where to store the input. However, your version has "bin[x]=scanf..." So you're assigning the return value of "scanf()" to "bin[x]", overwriting the value you just read. What is the return value of "scanf()"?



scanf()

So "scanf()" returns the number of items it successfully read. In your case, entering one integer at a time as expected, "scanf()" returns that number of items (one) successfully read.

That's where your array is being filled with all ones!

The solution, as stahta01 pointed out in post #2, is to change that line to: scanf("%d", &bin[x]);
(i.e. get rid of the "bin[x]=" part).

And that, my friend, is how we troubleshoot.

removed the bin[x], now it works fine. Thanks.

To be even more blunt: stop relying on guesswork to solve your problem.

Did you see [BEGINNER] tag in the post tittle? Maybe you didn't. I don't use guess work, I am learning so please guide if you want to.

Originally Posted by grumpy

Yes, I saw the beginner tag. There is a difference between guesswork and trying things out for learning purposes. Your approach in this thread is demonstrating guesswork. Hence my guidance to stop it.

Firstly, I write code accorfing to what I need. Secondly, I come here only after trying and eliminating all the bugs under my knowledge. So, if I didn't know that re-assigning bin[x] will give me a single value that's because I didn't know it as a beginner.

Originally Posted by Sankait Laroiya

Firstly, I write code accorfing to what I need.

What do you mean by this? Potentially, everyone codes according to their needs.

Secondly, I come here only after trying and eliminating all the bugs under my knowledge. So, if I didn't know that re-assigning bin[x] will give me a single value that's because I didn't know it as a beginner.

Instead of taking offense, try to look at it from his point of view -

Code:

bin[x]=scanf("%d", &bin[x]);

He probably thought that you would know about the return value of scanf() if you were going to use it in your code. Maybe you didn't understand what the return value of scanf() meant, but you could have tested your own assumption about what scanf() would return.

Test your assumptions when you debug. Then you won't be accused of guess work when you are stuck next time.

Originally Posted by Sankait Laroiya

Secondly, I come here only after trying and eliminating all the bugs under my knowledge.

Based on this thread, and the other one you just started, I think you should read the following link:

A development process

It describes how to write a program a little bit at a time, testing along the way.

For instance, if the first thing you need to do is get user input, then write code only to get the user input and print it out to the screen. Compile and test, verifying that you have read the expected values correctly. Then you can continue adding code, a little bit at a time, compiling and testing as you go.