Thread: HexToDec/DecToHex, feedback if any, Thanks.

Greetings EveryOne

I want to present you my Hexadecimal/Decimal converter for feedback.

HexToDec.c:

Code:

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <math.h>

int main()
{
	int	 StrMaxSize = 20;
	char *HexString = malloc(StrMaxSize);
	int  *HexNumbAt = malloc(StrMaxSize);
	char ValidHexNumber[16] = {'0', '1', '2', '3', '4', 
							   '5', '6', '7', '8', '9',
				   		   	   'a', 'b', 'c', 'd', 'e', 
						       'f'};

	int  CurrentStrSize = StrMaxSize-2;
	
	int DecNumb = 0;
	
	int NotValidHexValue = 0;
	
	unsigned int Cnt = 0;
	
	int i = 0;
	int k = 0;
	
	printf("Please Enter Your Hexadecimal Number: ");
	if(HexString != NULL && HexNumbAt != NULL)
	{
		int Char = EOF;
		
		while((Char = getchar()) != '\n' && Char != EOF)
		{
			// Input Hexadecimal Number;
			HexString[Cnt] = (char) Char;
			Cnt++;
			if(Cnt == CurrentStrSize)
			{
				CurrentStrSize = (Cnt+StrMaxSize)-2;
				
				HexString = realloc(HexString, CurrentStrSize);
				HexNumbAt = realloc(HexNumbAt, CurrentStrSize);
			}
		}
		HexString[Cnt] = '\0';
	}

	// Display the entered Hexadecimal Number;
	printf("HexNumber = %s\n", HexString);

		
	// Check for the validity of the entred Hexadecimal Number;
	for(i = 0; i < Cnt; i++)
	{
		char LowerCaseChar = tolower(HexString[i]);
		
		int j = 0;		
		for(j = 0; j < 16; j++)
		{
			if(LowerCaseChar == ValidHexNumber[j])
			{
				break;
			}
			
			if(j == 15)
			{
				NotValidHexValue = 1;
			}
		}
		
		if(NotValidHexValue)
		{
			printf("Error: Unrecognized Value\n");
			NotValidHexValue = 0;
			return -1;  // exit program with (-1);
		}
	}
	
	
	// Convert Hex to Dec;
	for(i=Cnt-1; i >= 0; i--)
	{
		int x = 0;
		
		if(isdigit(HexString[i]))
		{
			char Ch[2] = {0};
			Ch[0] = HexString[i];
			Ch[1] = '\0';
			x = atoi(Ch);
			
			HexNumbAt[i] = (x*pow(16,k));
		}
		
		if(isalpha(HexString[i]))
		{
			switch(tolower(HexString[i]))
			{
				case 'a':
					 x = 10;
					 HexNumbAt[i] = (x*pow(16,k));
					 break;
					case 'b':
						 x = 11;
						 HexNumbAt[i] = (x*pow(16,k));
						 break;
					case 'c':
						 x = 12;
						 HexNumbAt[i] = (x*pow(16,k));
						 break;
					case 'd':
						 x = 13;
						 HexNumbAt[i] = (x*pow(16,k));
						 break;
					case 'e':
						 x = 14;
						 HexNumbAt[i] = (x*pow(16,k));
						 break;
					case 'f':
						 x = 15;
						 HexNumbAt[i] = (x*pow(16,k));
						 break;
				}
		}
		k += 1;
		DecNumb += HexNumbAt[i];
	}

	// Display the Decimal converted number;
	printf("DecNumb = %d\n", DecNumb);
	
	return 0;
}

DecToHex.c:

Code:

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <math.h>

int main()
{
	int    DecNumb     = 0;
	char   HexNumb[20] = {0};
	double Quotient = 1;
	int	   Reminder = 0;
	
	printf("Please Enter A Decilam: ");
	scanf("%d", &DecNumb);
	
	int i = 0;
	Quotient = DecNumb;
	while(Quotient != 0)
	{
		Reminder = ((int) Quotient)%16;
		Quotient = Quotient/16;
		
		Quotient = (int) Quotient;
		
		if(Reminder >= 0 && Reminder <= 9)
		{
			sprintf(&HexNumb[i], "%d", Reminder);
		}
		else
		if(Reminder >= 10 && Reminder <= 15)
		{
			switch(Reminder)
			{
				case 10: HexNumb[i] = 'A'; break;
				case 11: HexNumb[i] = 'B'; break;
				case 12: HexNumb[i] = 'C'; break;
				case 13: HexNumb[i] = 'D'; break;
				case 14: HexNumb[i] = 'E'; break;
				case 15: HexNumb[i] = 'F'; break;
				default: printf("Error: Unrecognized Hex Digit\n");
						 printf("Reminder = %d", Reminder);
						 return -1;
						 
			}
		}
		
		i++;
	}
	HexNumb[i] = '\0';
	
	printf("HexNumb = ");
	while(i >= 0)
	{
		printf("%c", HexNumb[i]);
		i--;
	}
	printf("\n");
	return 0;
}

Thank You for your feedback if there is any

Sorry, I couldn't help myself...

hextodec.c:

Code:

#include <stdio.h>

int main(void)
{
	int val;	
	printf("Enter a hexadecimal number: ");	
	scanf("%x", &val);
	printf("%d\n", val);
	
	return 0;
}

dectohex.c:

Code:

#include <stdio.h>

int main(void)
{
	int val;	
	printf("Enter a decimal number: ");	
	scanf("%d", &val);
	printf("%x\n", val);
	
	return 0;
}

As for comments, one thing I noticed is that you didn't use character - '0' to get digits. The possibility of non-ASCII character sets aside, (I haven't seen any on a modern system, have you?) it's a neat trick to know for a quick digit-to-character or character-to-digit conversion.

As for comments, one thing I noticed is that you didn't use character - '0' to get digits. The possibility of non-ASCII character sets aside, (I haven't seen any on a modern system, have you?) it's a neat trick to know for a quick digit-to-character or character-to-digit conversion.

I don't understand what you are talking about can you explain further please.

Thanks for your reply.

Characters are laid out contiguously and in order '0' through '9', so, eg. (int)('0' - '0') = 0, and (int)('5' - '0') = 5.
Given a character 'n' representing some digit 0-9, (int)('n' - '0') = n. It's just something I prefer over functions life sscanf() or atoi() in this particular case.

Originally Posted by bernt

Characters are laid out contiguously and in order '0' through '9', so, eg. (int)('0' - '0') = 0, and (int)('5' - '0') = 5.
Given a character 'n' representing some digit 0-9, (int)('n' - '0') = n. It's just something I prefer over functions life sscanf() or atoi() in this particular case.

I understand now, Thank you very much for the tip

P.S: i would been got it the first time if it was presented like this:
one thing I noticed is that you didn't use (character - '0') to get digits.

That's why i got confused, Thank you again.

I don't like this way of doing things as they are not portable. Sure, it will work on most systems used today, but what about 2 years from now? I mean, there are other encoding systems then ASCII... If there are a standard library function to convert things, then use it. I don't know how many times I have fixed bugs in peoples code that stem from people making assumptions. Stuff like assuming an int is a certain length, that you can represent the date with 2 digits and that you can do - '0' to get a digit, they are _all_ bad. Sorry if my tone sounds kind of harsh, it is not meant to, but I think it is better to learn that lesson sooner rather than later and this way rather than the hard way.

I agree with you on this Jimmy, and i had read something similar to this matter, like that an int may be presented in the memory with 2-bits or 4-bits, it can all be dependent from computer to another, thank you for the note.