// Binary to Decimal, Hexadecimal and Octal conversion program
// tested with Pelles C     vegaseat     15dec2004
 
#include <stdio.h>
#include <string.h>
 
int bin2dec(char *bin);
 
int main()
{
  char bin[80] = "";
  char *p;
  int  dec;
 
  while(strcmp(bin,"0")) 
  {
    printf("\n Enter a binary number (just 0 to EXIT): ");
    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  Hexadecimal = 0x%04X  Octal = 0%o\n",dec,dec,dec);
  }
 
  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");
      return (0);
    }
    for(b = 1, m = len; m > k; m--) 
    {
      // 1 2 4 8 16 32 64 ... 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);
}