Converting hexadecimal to binary

[codemunkee]

I am going to make a program that will convert from hexadecimal string, then to binary and finally to decimal. Now here's the problem (i guess) : when I try to convert hexadecimal string to binary string, I just did a "cout" and this is not a binary string. So, what am I exactly going to do to make a binary string from my hexadecimal string? I don't know what to do, I tried my best for days but still, there's no improvement.. T_T

#include <iostream>
#include <string.h>
#include <conio.h>
using namespace std;


//this function is for my hexadecimal input, to filter the keys from the keyboard
char* hex (char str1[])
{

     int i=0,x=0;  
     do{         
             str1[x]=getch();
             str1[x]=toupper (str1[x]); 
                if (((str1[x]>='0') && (str1[x]<='9')) || ((str1[x]>='A') && (str1[x]<='F'))){
                    cout<<str1[x];
                    x++;
              }
               
         
    }while (str1[x]!=13);
    str1[x]='\0';
return str1;
}

//and this function is for my binary to decimal function.
int bd (char bin[]){
 
     int c,x=0,i,factor=1;
     int decimal=0;
     int len;
    
     len = strlen (bin)-1;
     
     for (i=0;i<=len;len--){
            if (bin[len]==49){
               c=bin[len]-48;}
            else if (bin[len]==48){
               c=bin[len]-48;}
         decimal = decimal + c*factor;
         factor = factor*2;
     }     
    return decimal; 
}

main (void)
{
     int i;
     char s[40];
     hex (s);
     
     //this is for my hexadecimal to binary (the part where I need help T_T)
      for(i=0;s[i]!='\0';i++)
		 {
   
          switch(s[i])
		   {
		    case '0':
		     cout<<"0000";
		     break;
		    case '1':
		     cout<<"0001";
		     break;
		    case '2':
		     cout<<"0010";
		     break;
		    case '3':
		     cout<<"0011";
		     break;
		    case '4':
		     cout<<"0100";
		     break;
		    case '5':
		     cout<<"0101";
		     break;
		    case '6':
		     cout<<"0110";
		     break;
		    case '7':
		     cout<<"0111";
		     break;
		    case '8':
		     cout<<"1000";
		     break;
		    case '9':
		     cout<<"1001";
		     break;
		    case 'A':
		     cout<<"1010";
		     break;
		    case 'B':
		     cout<<"1011";
		     break;
		    case 'C':
		     cout<<"1100";
		     break;
		    case 'D':
		     cout<<"1101";
		     break;
		    case 'E':
		     cout<<"1110";
		     break;
		    case 'F':
		     cout<<"1111";
		     break;
		   }
		  }
system ("PAUSE");
return 0;
}

:((

[weaknessforcats]

Presumably by a binary string you mean a char string with only 1 and 0 characters.

That being the case, just use a string object.

Your cout << "0101" would become:

string str;
//etc...

str += "0101";

[whodgson]

Converting hexadecimal to binary is really quite simple:
Just convert each hexadecimal character to its four digit binary equivalent.
so 0xff = 1111 1111
or 0x27b=0010 0111 1011 //I have left spaces so that it easier to read
so write the code that will accomplish this and half the problem is solved

[donbock]

Hexadecimal digits can be upper or lower case. That is, you should for example check for both 'A' and 'a'. Alternatively, you could switch on toupper(s[i]).