DaniWeb Forum Index > Software Development > C

C RSS

Exercise using: unsigned char bcd(int n);

•

Join Date: Sep 2004

Posts: 421

Reputation: JoBe is on a distinguished road

Solved Threads: 4

JoBe

Offline

Posting Pro in Training

Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

Hi ladies and gents,

Next exercise is the following:

Write the function which we can declare as follows:
unsigned char bcd (int n);

The idea of this function is to store the last two decimal numbers of n into a 'binary coded decimal' byte and to return this value. So, when n would be equal to 12345, then the 4 and the 5 from this number would be encoded into the 8 bits as:

0100 0101

Now, I tried to use the code Narue gave me, to cut the decimal number into pieces like this:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
int main()
{
	int a = 12345;
	int x;
 
	x = bcd(a);
	cout << x <<endl;
 
	return 0;
}
 
unsigned char bcd (int n)
{
	int i;
	char totvalue;
	ostringstream out;
 
	out<< n;
	string s = out.str();
 
	for (i = 1; i >= 1; --i)
	{			
		totvalue = s[i] - '0';
                          start changing decimal number into binary code...
	}
	return totvalue;
}
int main()
{
	int a = 12345;
	int x;

	x = bcd(a);
	cout << x <<endl;

	return 0;
}

unsigned char bcd (int n)
{
	int i;
	char totvalue;
	ostringstream out;

	out<< n;
	string s = out.str();

	for (i = 1; i >= 1; --i)
	{			
		totvalue = s[i] - '0';
                          start changing decimal number into binary code...
	}
	return totvalue;
}

THis way, I can get the separate values of that decimal number and then try to change them into a binary code?
Thing is, I'm not sure this is actually the correct/best way of dealing with this?

Questions are,
1) could someone show me wich is the best way to deal with this and keeping in mind that I have to use:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
unsigned char bcd (int n);
unsigned char bcd (int n);

2) Problem occurs is, that how can I return two separate pieces of binary code: first 0101 and then 0100 or is it 0100 and then 0101. Quiete frankly, I don't understand how this is accomplished. Or do you have to send it in one time 0100 0101?

3) Also, how can an unsigned char return a binary code 0100 0101?

Thanks for the help guys, maybe the solution is made out of the several exercises I allready made in wich you helped me aswell, but I just don't see how I can solve it :-|

•

Join Date: Sep 2004

Posts: 7,614

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

>out<< n;
>string s = out.str();
In this case (since you're taking the rightmost digits) arithmetic operations may be easier:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
if ( n >= 10 ) { // Make sure there are two digits
  int a = n % 10;
  int b = ( n / 10 ) % 10;
}
if ( n >= 10 ) { // Make sure there are two digits
  int a = n % 10;
  int b = ( n / 10 ) % 10;
}

>how can I return two separate pieces of binary code
It's an exercise in bit packing. The two 4 bit chunks are packed together in an unsigned char:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
( b << 4 ) | a
( b << 4 ) | a

>3) Also, how can an unsigned char return a binary code 0100 0101?
The char type has to be at least 8 bits by definition, so you can easily fit two 4 bit pieces there.

I'm here to prove you wrong.

•

Join Date: Sep 2004

Posts: 421

Reputation: JoBe is on a distinguished road

Solved Threads: 4

JoBe

Offline

Posting Pro in Training

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

Well, thanks for the help Narue,

With the code you showed, I managed to make this:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
unsigned char bcd (int n);
 
int main()
{
	int value = 12345;
	int x;
 
	x = bcd(value);
	cout << x <<endl;
 
	return 0;
}
 
unsigned char bcd (int n)
{
	char binary[80], temp[80], code;
	int remain = 0, decimal = 0;
	int a, b, i, k = 0;
 
	if (n >= 10)
	{
		a = n % 10;
		b = (n / 10) % 10;
	}
 
	for (i = 0; i < 2; ++i)
	{
		if (i == 0)
			decimal = a;
			else
			decimal = b;
 
			do
			{
				remain = decimal % 2;
				decimal = decimal / 2;
				temp[k++] = remain + 0x30;
			}
			while (decimal > 0);
 
				while (k >= 0)
				{
					binary[n++] = temp[--k];
				}
				binary[n-1] = 0;             
 
				code = ( binary[n] << 4 ) | binary[n];
	}
 
	return code;
}
unsigned char bcd (int n);

int main()
{
	int value = 12345;
	int x;

	x = bcd(value);
	cout << x <<endl;

	return 0;
}

unsigned char bcd (int n)
{
	char binary[80], temp[80], code;
	int remain = 0, decimal = 0;
	int a, b, i, k = 0;

	if (n >= 10)
	{
		a = n % 10;
		b = (n / 10) % 10;
	}

	for (i = 0; i < 2; ++i)
	{
		if (i == 0)
			decimal = a;
			else
			decimal = b;

			do
			{
				remain = decimal % 2;
				decimal = decimal / 2;
				temp[k++] = remain + 0x30;
			}
			while (decimal > 0);

				while (k >= 0)
				{
					binary[n++] = temp[--k];
				}
				binary[n-1] = 0;             

				code = ( binary[n] << 4 ) | binary[n];
	}

	return code;
}

Problem is that alltough I'm not getting any error messages, when I debug the program and get towards this part of the program:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
	binary[n++] = temp[--k];
	binary[n++] = temp[--k];

I get a message: Unhandled exception in LAOef4_6.exe: 0xC0000005: Access Violation :o

I'm assuming I did something seriously wrong here, tough it doesn't crash the program

•

Join Date: Sep 2004

Posts: 7,614

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

>0xC0000005: Access Violation
An access violation means you tried to access memory outside of your address space. After debugging lots of these problems, you begin to get a sense for what memory addresses look "wrong" for what you're trying to do. 0xC0000005 looks wrong, and most likely one of your indices is accessing an array out of bounds.

Of course, your solution is way too long. You could practically paste the code I gave you into your function body and be set:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
unsigned char bcd ( int n )
{
  if ( n >= 10 ) { // Make sure there are two digits
    int a = n % 10;
    int b = ( n / 10 ) % 10;
 
    return ( b << 4 ) | a;
  }
 
  return n;
}
unsigned char bcd ( int n )
{
  if ( n >= 10 ) { // Make sure there are two digits
    int a = n % 10;
    int b = ( n / 10 ) % 10;

    return ( b << 4 ) | a;
  }

  return n;
}

I'm here to prove you wrong.

•

Join Date: Sep 2004

Posts: 421

Reputation: JoBe is on a distinguished road

Solved Threads: 4

JoBe

Offline

Posting Pro in Training

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

>Of course, your solution is way too long. You could practically paste the code I gave you into your function body and be set:

Well, I did use your code, but using it solely doesn't make the decimal number into a binary code, that's why I used the remaining code?

•

Join Date: Sep 2004

Posts: 7,614

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

>but using it solely doesn't make the decimal number into a binary code
The binary code is packed inside an unsigned char. The only way to get it out is to access the value bit by bit:

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
while ( value != 0 ) {
  cout<< !!( value & 1 );
  value >>= 1;
}
while ( value != 0 ) {
  cout<< !!( value & 1 );
  value >>= 1;
}

You're confusing a binary code with the string representation of a binary code.

I'm here to prove you wrong.

•

Join Date: Apr 2004

Posts: 4,342

Reputation: Dave Sinkula has a brilliant future

Solved Threads: 237

Dave Sinkula Dave Sinkula is offline

Offline

long time no c

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

I was under the impression that the return value might be expected to be an unsigned int, and that the expected input/output might be as follows.

Help with Code Tags

(Toggle Plain Text)

#include <stdio.h>

unsigned int dec2bcd(unsigned int dec)
{
   unsigned int bits, bcd = 0;
   for ( bits = 0; dec; bits += 4, dec /= 10 )
   {
      bcd |= dec % 10 << bits;
   }
   return bcd;
}

int main()
{
   unsigned int value = 12345, result = dec2bcd(value);
   printf("bcd(%u) = 0x%X [%u]\n", value, result, result);
   return 0;
}

/* my output
bcd(12345) = 0x12345 [74565]
*/

Or am I just off today?

"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand

•

Join Date: Sep 2004

Posts: 421

Reputation: JoBe is on a distinguished road

Solved Threads: 4

JoBe

Offline

Posting Pro in Training

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

Dave and especially Narue,

Thanks for the help, but I'm giving up on this, I simply am not getting what is asked in this exercise and the pieces of code you are giving me Narue are just confusing me more and more and instead of leading me to the solution is getting me further and further away :!:

To say it as it is, I'm just not cut out for this, I hoped to learn this as a fun hobby, but actually is getting me frustrated as it's not working out as it should.

STill, you guys are top notch and I enjoyed learning from you tough I didn't remember all of it and certainly so it seems didn't understand all of it

•

Join Date: Sep 2004

Posts: 7,614

Reputation: Narue has a reputation beyond repute

Solved Threads: 713

Narue

Offline

Code Goddess

Re: Exercise using: unsigned char bcd(int n);

Mar 31st, 2005

>but I'm giving up on this
Not totally I hope. You've shown a lot of promise. Programming is hard. There's no getting around it, so you just have to keep going until you finally have a flash of insight and understand what was confusing you. Then you can move on to a new thing that confuses you. This process is repeated until you die.

I'm here to prove you wrong.

•

Join Date: Apr 2004

Posts: 4,342

Reputation: Dave Sinkula has a brilliant future

Solved Threads: 237

Dave Sinkula Dave Sinkula is offline

Offline

long time no c

Re: Exercise using: unsigned char bcd(int n);

#10

Mar 31st, 2005

http://en.wikipedia.org/wiki/Binary_coded_decimal

 Help with Code Tags 
 C Syntax (Toggle Plain Text) 
Decimal        Binary Coded Decimal    BCD (Hex)  BCD (Decimal)
 12345   ->  0001 0010 0011 0100 0101   0x12345       74565
Decimal        Binary Coded Decimal    BCD (Hex)  BCD (Decimal)
 12345   ->  0001 0010 0011 0100 0101   0x12345       74565