# Converting Binary to Decimal

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### #1 browngod2002

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# Converting Binary to Decimal

Posted 24 September 2006 - 01:04 PM

I am trying to convert a binary number input by a user into a decimal number. I know how to so it on paper but getting C to do it I am lost. I am using Dev-C compiler. Here is what I got so far.

```#include<stdio.h>
#include<math.h>
#include<string.h>

int bin2dec(int decimal);

int main(void)
{
int num;

printf("The decimal equilavent is: %d", bin2dec(decimal));

getchar();
getchar();
return 0;
}

int bin2dec(int decimal)
{
int num[10];
int i;
int bin;
int arr1[10];
int arr2[10] = {512,256,128,64,32,16,8,4,2,1};

printf("Enter a binary(0's and 1's) number: ");
scanf("%d", &arr1);

This is qheere I get confused.
for (i = 0; i < arr1; i++)
{
if (arr1[i] == 1)
num[i] = arr1[i];
arr2[i]= num[i]
decimal = arr2[i];
}

return decimal;
}
```

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## Replies To: Converting Binary to Decimal

### #2 Israel

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## Re: Converting Binary to Decimal

Posted 24 September 2006 - 09:46 PM

Ok, I'm not even going to pretend to know how to answer your question. I know a little C++ but I think your beyond me here. But if I were you I might view a web page like this which does the same thing with javascript and maybe look at how some of the functions they used worked. I know don't know if this will help you but good luck.
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### #3 dorknexus

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## Re: Converting Binary to Decimal

Posted 25 September 2006 - 01:02 AM

the following snippet contains functions which convert alpha-numeric values (which are decimal representations of letters) into binary. and towards the bottom of that snippet post, there are functions which convert binary back into the decimal values.

http://code.dreaminc...t/snippet30.htm

be aware that this takes binary in the form of right-to-left, meaning that the decimal value 2 is represented as 01.

whereas the left-to-right form would represent 2 as 10
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### #4 born2c0de

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## Re: Converting Binary to Decimal

Posted 25 September 2006 - 06:28 AM

Always use the Bitwise AND Operator for such conversions.
```int i, ch;
printf("Enter an integer: ");
scanf("%c",&ch);
for(i=0x80; i;i=i>>1)
printf("%d", ( (ch&i) ? 1 : 0 ) );

```

You can also use the itoa function to do this.
```/*
i is the number to be converted
c is the buffer (char[]) where the binary number is stored.
2 represents the base which the source (ie. i ) has to be converted into.
*/
itoa(i,c,2);
printf("%s",c);

```

If you can see something in the Previous code that used the For loop, you will see the possibility of using a recursive function to do this.
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### #5 browngod2002

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## Re: Converting Binary to Decimal

Posted 25 September 2006 - 07:54 AM

Thank you born2c0de that was helpful
I am new so somethings seems difficult than they are.

This post has been edited by Dark_Nexus: 25 September 2006 - 08:46 AM

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### #6 browngod2002

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## Re: Converting Binary to Decimal

Posted 25 September 2006 - 05:05 PM

I am trying to convert bin to dec without putting it into an array or a string here is the code I have so far. I need someone to tell me why it is not working. I am using VC++ 2005 Express Edition.

```#include "stdafx.h"
#include <stdio.h>
#include<math.h>

int bin2dec(int decimal);

int main()
{
int decimal;

printf("Enter an integer: ");
scanf_s("%c",&decimal);

printf("The decimal equivalent = %d\n",bin2dec(decimal));

getchar();
getchar();
return 0;
}

int bin2dec(int decimal)
{
int total = 0;
int power = 1;

while(decimal > 0)
{
total += decimal % 10 *power;
decimal = decimal / 10;
power = power * 2;
}

return decimal;
}
```

This post has been edited by browngod2002: 25 September 2006 - 05:15 PM

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### #7 Jayman

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## Re: Converting Binary to Decimal

Posted 25 September 2006 - 05:59 PM

I believe the problem lies here scanf_s("%c",&decimal); (although I did not put this in a compiler to check it). Your variable decimal is of type integer, but you are using the character format specifier. Change your format specifer to match your variable type.

```scanf_s("%d",&decimal);

```

It would be of great benefit if you describe in what way your application is not working, so that someone can better help you.

List error messages, incorrect output, compilation errors.
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### #8 Vagabond

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## Re: Converting Binary to Decimal

Posted 26 September 2006 - 03:05 AM

This is a small program I wrote some time ago I don't know if the concepts will help.
```

snippet......

switch(choise)
{
case 1: cout << "Enter a Hex number: ";
cin  >> hex >> number;
cout << "\n   value in octal = "
<< oct << number << endl;
cout << " value in decimal = "
<< dec << number << endl;
break;
case 2: cout << "Enter a Octal number: ";
cin  >> oct >> number;
cout << "\n	   value in hex = "
<< hex << number << endl;
cout << "   value in decimal = "
<< dec << number << endl;
break;
case 3: cout << "Enter a dec number: ";
cin  >> dec >> number;
cout << "\n   value in octal = "
<< oct << number << endl;
cout << "	 value in hex = "
<< hex << number << endl;
break;
case 4:  cout << "Program terminated by user...";
exit(0);
default : cout << "ERROR ~ Invalid selection\n\n";
break;
}

```

If there arn't any objections I can put the compelted code up if you wish.

This post has been edited by Vagabond: 26 September 2006 - 03:17 AM

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### #9 browngod2002

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## Re: Converting Binary to Decimal

Posted 26 September 2006 - 11:49 AM

When I build and run the program I get no errors or warnings but the output is all wrong. I think it is in my formula but I can't get the formula to work right.Here is the updated code.

```#include "stdafx.h"
#include <stdio.h>
#include <math.h>

/* function prototype */
int bintodec(int decimal);

int _tmain(int argc, _TCHAR* argv[])
{
int decimal;

printf("Enter an interger (0's and 1's): ");
scanf_s("%d", &decimal);

printf("The decimal equilavent is %d.\n", bintodec(decimal));

getchar();
getchar();
return 0;
}

int bintodec(int decimal)
{
int total = 0;
int power = 1;
int number = 0;

decimal--;
while(decimal >=0)
{
/* this is where the problem is I need some advice on how to fix it.*/

total += decimal % 10 * power;
decimal = decimal / 10;
power = power * 2;
number += decimal;
decimal--;
}

return number;
}
```

This post has been edited by Dark_Nexus: 26 September 2006 - 09:54 PM

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### #10 Jayman

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## Re: Converting Binary to Decimal

Posted 26 September 2006 - 11:54 AM

Maybe the following link will help explain how to convert.

http://www.is.wayne....inary/page3.htm
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### #11 browngod2002

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## Re: Converting Binary to Decimal

Posted 26 September 2006 - 03:50 PM

Thank all of you that helped me figure this problem out. I was returning the wrong value in my function(returning decimal instead of total). Here is my finished code and I have also posted it in the code snippets page for future user that may have the same problem that i did.

```#include "stdafx.h"
#include <stdio.h>
#include <math.h>

/* function prototype */
int bintodec(int decimal);

int _tmain(int argc, _TCHAR* argv[])
{
int decimal;

printf("Enter an interger (0's and 1's): ");
scanf_s("%d", &decimal);

printf("The decimal equilavent is %d.\n", bintodec(decimal));

getchar();
getchar();
return 0;
}

int bintodec(int decimal)
{
int total = 0;
int power = 1;

while(decimal > 0)
{
total += decimal % 10 * power;
decimal = decimal / 10;
power = power * 2;
}

return total;
}
```

This post has been edited by browngod2002: 26 September 2006 - 03:52 PM

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### #12 boelegg52

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## Re: Converting Binary to Decimal

Posted 20 September 2010 - 08:54 PM

Thanks everybody for the information on converting binary to decimal
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### #13 CTphpnwb

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## Re: Converting Binary to Decimal

Posted 20 September 2010 - 09:01 PM

Belated, but here's a more generic method I wrote.

```#include <iostream>
#include <math.h>
using namespace std;
int bin, decimal = 12, decimal2;
int base_one = 10, base_two = 2;
int convert(int num, int starting_base, int destination_base);
int main (int argc, char * const argv[]) {
bin = convert(decimal, base_one, base_two);
cout << "Base"<< base_one<< " "<< decimal << " = Base"<< base_two<< " " << bin << endl;
decimal2 = convert(bin, base_two, base_one);
cout << "Base"<< base_two << " " << bin << " = Base"<< base_one << " " << decimal2 << endl;
return 0;
}
int convert(int num, int starting_base, int destination_base)
{
int val = 0, count = 0;
while (num) {
val += pow(starting_base, count) * (num % destination_base);
count++;
num /= destination_base;
}
return val;
}
```

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