Converting array of binary numbers to decimal

Question

I am trying to convert an array of binary characters to Decimal. My code looks something like this:

int main(int argc, char** argv) {
   int STRING_SIZE = 32;
   int stringLength = 0; 
   char input[STRING_SIZE];
   int arrayCounter = 0; 
   int base = 0;
   char decimalValue[stringLength];
   int exponent = 0;
   int remainder[stringLength];

printf("\nPlease enter a Binary, Decimal or Hexadecimal value no longer than 32 characters. ");
scanf("%s", input);
fgetc(stdin);

//Count the length of the string.
while (input[stringLength] != 0) { 
    printf("%c", input[stringLength]);
    stringLength++;
 }

for (arrayCounter = 0; arrayCounter != stringLength; arrayCounter++) {
    remainder[arrayCounter] = input[arrayCounter] - '0' / 10;
    decimalValue[arrayCounter] = decimalValue[arrayCounter] + remainder[arrayCounter] * base;
    input[arrayCounter] = input[arrayCounter] / 10;
    base = base * 2;
    printf("%c", decimalValue[arrayCounter]);
 }

printf("%s", decimalValue);



return (EXIT_SUCCESS);
}

I know how to convert between binary and Decimal, but I am extremely confused on how to convert binary to decimal when the input is an array of characters.

So do I understand it correctly, that you are trying to convert a c_string (char[]) representing a binary number into a new string representing a decimal number? — visibleman
– visibleman, Commented Mar 28, 2018 at 4:16
Yes, I want to convert the string into a new string representing the decimal value. E.g input: 10 (binary), output: 2 (decimal) — B Robert
– B Robert, Commented Mar 28, 2018 at 4:20
Is there some specific reason you want to implement this yourself? Otherwise, I recommend using strol() with base 2 [cplusplus.com/reference/cstdlib/strtol/] to turn the string to an integer, and then sprintf to turn the integer back to a string. — visibleman
– visibleman, Commented Mar 28, 2018 at 4:27
Part of an assignment, our teacher wants us to implement it ourselves. — B Robert
– B Robert, Commented Mar 28, 2018 at 4:31
You never convert input[arrayCounter] from ASCII to decimal, e.g. input[arrayCounter] -= '0', you do for remainder, but not for the stored character. (you should use another variable also rather than changing the character value -- but that's up to you) — David C. Rankin
– David C. Rankin, Commented Mar 28, 2018 at 4:34

Pras · Accepted Answer · 2018-03-28 04:41:38Z

4

There was similar question asked(Binary to Decimal and Hex (bit by bit) ) where I had replied to use formula below to convert binary chars to decimal

2^7 * (1 OR 0) + 2^6 * (1 OR 0) + 2^5 * (1 OR 0) + 2^4 * (1 OR 0) + 2^3 * (1 OR 0) + 2^2 * (1 OR 0) + 2^1 * (1 OR 0) + 2^0 * (1 OR 0)

Below is the sample code you can refer that does it, you can take bstr in input instead of initializing at declaration

#include<math.h>
#include<stdio.h>
#include<string.h>
int main()
{
char bstr[]="10011";
int i=0;
int len  = strlen(bstr);
int sum = 0;
int j = 0;

for(i=(len-1);i>=0;i--)
{
    sum = sum + (pow(2,i) * (bstr[j] - '0'));
    j++;
}
printf("decimal = %d\n",sum);
return 0;
}

edited Mar 28, 2018 at 4:41

answered Mar 28, 2018 at 4:33

Pras

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7 Comments

B Robert Over a year ago

I tried to implement this, but I am receiving a different output.

for (i= stringLength- 1; i >= 0; i--) {         decimalValue = decimalValue + (power(2, i)) * (input[arrayCounter] - '0');         arrayCounter++;     }          printf("\n%d", decimalValue);

INPUT: 10 Output: 112

Pras Over a year ago

Are you sure decimalValue is initialized to 0

B Robert Over a year ago

Just checked, I had it initialized as a Char, changed it to Int and it is initialized to 0. Output now returns -144 when input 10.

Pras Over a year ago

arrayCounter is it initialized to zero? you would have to debug to see whats going wrong

B Robert Over a year ago

Of course that was the problem! Thank you so much for your help!

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