made this binart yo decimal converter and i want to make it smaller and more compact

[al3x748769]

hey,
i made this a few years ago. i want to take the error when u enter a different number and would like to make it more compact. can you guys help me make it smaller. this is a 8 bit binary to decimal converter.

#include <stdio.h>
      #include <string.h>
   
       
   
      int bin2dec(char *bin);
   
       
   
      int main()
  
      {
  
      char bin[9] = "";
  
      char *p;
  
      int dec;
  
       
  
      while(strcmp(bin,"0"))
  
      {
  
      printf("\n Enter a binary number (just 0 to EXIT): ");  //Enter number to be converted in binary form
  
      fgets(bin, sizeof(bin), stdin);
  
      // check for and remove trailing \n
  
      if ((p = strchr(bin,'\n')) != NULL)
  
      {
  
      *p = '\0'; 
  
     }
  
      dec = bin2dec(bin);
  
      if (dec) printf("\nDecimal = %d \n",dec); //Display Converted # in Decimal,
  
      }
  
       
  
      getchar(); // wait
  
      return 0;
  
      }
  
      
  
      // convert a binary string to a decimal number, returns decimal value
  
      int bin2dec(char *bin)
  
      {
  
      int b, k, m, n;
  
      int len, sum = 0;
  
       
  
      len = strlen(bin) - 1;
  
      for(k = 0; k <= len; k++)
  
      {
  
      n = (bin[k] - '0'); // char to numeric value
  
      if ((n > 1) || (n < 0))
  
      {
  
      puts("\n\n ERROR! BINARY has only 1 and 0!\n"); //Error if anything other than 1 or 0 entered
  
      return (0);
  
      }
  
      for(b = 1, m = len; m > k; m--)
  
      {

      // 1 2 4 8 16 32 64 128 ... place-values, reversed here

      b *= 2;	// 
 
      }
  
      // sum it up
 
      sum = sum + n * b;
 
      //printf("%d*%d + ",n,b); // uncomment to show the way this works

      }

      return(sum);
 
      }

[death_oclock]

Instead of this:

for(b = 1, m = len; m > k; m--)
{
// 1 2 4 8 16 32 64 128 ... place-values, reversed here
b *= 2;
}
// sum it up
sum = sum + n * b;

Include <math.h>
and replace your the previously mentioned code with this:

sum += n * (int)pow(2, k);

[Salem]

> and replace your the previously mentioned code with this:
> sum += n * (int)pow(2, k);
Bad idea.
a) it's slower
b) you're at the mercy of whatever inaccuracies are inherent in the floating point library.

> can you guys help me make it smaller.
Sure
a) use code tags - something you're consistently failing to do
b) strip out the excess of newlines
c) learn to indent code.
It's horrible.

[Murtan]

Well, if you're not afraid of pointers...

int bin2dec(char * bin)
{
    int n;
    int sum = 0;
    while (*bin) 
    {
        n = *bin - '0';
        if (n < 0 || n > 1)
        {
            printf("\nInvalid binary character: '%c'\n", *bin);
            puts("Binary only uses the digits 0 and 1.\n");
            return 0;
        }
        // double what we had before and add a new low bit
        sum = (sum << 1) + n;
        ++bin;
    }
    return sum;
}

I'm really hoping this wasn't homework, you might be hard-pressed to explain where the idea came from :)