converting hex to dec

hey guys i've got a conversion here but it is not displaying correctly.

it is making the large hexadecimal numbers into negative decimal numbers.

also when displaying a hex number with a 0 at the front it isn't leaving displaying the 0, i need it to.
(its reading these numbers from a file.

this is the code.
thanks guys..

Code:

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


FILE * inputdata;

void openfile(void);




int main()
{

	openfile();
	
	return (0);
}




void openfile(void)
{


	unsigned int hex;
	int i=0;

	inputdata = fopen("numbers.txt","r");

	if (inputdata==NULL)
	{ 
		printf("File cannot be opened for reading");
	} 

	printf("Line #	Hex		Decimal		Binary\n");

	while (fscanf(inputdata,"%x",&hex) != EOF)
	{
		
		
		printf("%i	%x	%d\n",i , hex , hex);
		i++;
		

	}
}

You seem to have your function prototypes backwards. main always returns an int, and since you don't actually do anything with the return value of open_file (which is very poorly named, IMO), it may as well be void.

The globals are sloppy, and you don't provide any example of your input file either.

Quzah.

edited now. thanks

> while (fscanf(inputdata,"%x",&hex) != EOF)
Only works if your file consists only of hex numbers
Anything unexpected will cause your program to loop forever

while (fscanf(inputdata,"%x",&hex) == 1)
is a better test

> it is making the large hexadecimal numbers into negative decimal numbers.
Use %u in place of %d

> also when displaying a hex number with a 0 at the front it isn't leaving displaying the 0
How about
%#x
when printing the hex then

Or
0x%x

salem thanks for your help.
still have a problem with the last thing..

i'm reading hex numbers from a file, for example 00032ad45
and the %#x hasn't fixed me there..
i'll keep trying but any help would be great.

all numbers i'm importing from the file are 32 bit numbers

eg 12a44d72

thanks

______________
edit : worked it out.
thanks anyway!

ok, i'm attempting to change my code to read into a 2 dimensional array now. so i'll go into more depth.

there is a 40 of 32 bit hexadecimal numbers in a file.

eg.
12a44d72
4d72608f
.
.
.
980c2983

so i'm attempting to read those from the files into a two dimensional array, but i've got an error which i can't figure out.

this is the new updated code.

Code:

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


FILE * inputdata;

void readfromfile(void);




int main()
{

	readfromfile();
	
	return (0);
}




void readfromfile(void)
{

	unsigned int hex[40][8],i,j;

	inputdata = fopen("numbers.txt","r");

	if (inputdata==NULL)
	{ 
		printf("File cannot be opened for reading");
	} 

	printf("Line #	Hex		Decimal		Binary\n");

	for (i=0; i<40; i++)
	{
		if (hex == " ")
		{
			break;
		}

		for (j=0; j<8; j++)
		{
			fscanf(inputdata,"%d", hex[i][j]);	
		}
    }
}

Well if you want your output to match your input, then store it in a string
Use fgets() to read the file in the first instance, then use sscanf() to extract information from the resulting string.

There is no point in storing all your input in an array.

sorry the reason i want to store it in an array is to then convert it into binary, which i'm not all that sure about anyway.

but i was thinking that if its in a two dimensional array i can use a switch statement to look at each individual number and then assign a binary value to match..
if that makes sense..

you wouldn't know a better way would you?

you've been very helpful so far, thanks.

What would be the purpose of the two dimensions then? Also, you're saying you're going to read each individual character in the file then? It is most definately easier to just read the entire value at once, as you're doing with fscanf or the fgets/sscanf combo, than it is to read each individual character and assemble the number yourself.

I'm still not sure of what you intend to do with the two dimensions. Perhaps you could throw together a bit of pseudocode to explain your intentions?

Quzah.

well i'm not sure of the best way to convert the hexadecimal into binary code.
so i thought what i would do is look at each part of the number individually..
eg.

12a44d72
would be broken into blocks of
|1|2|a|4|4|d|7|2|
and then converted like
|0001||0010|1010|0100|0100| etc..

but there is possibly a better way of doing it?

Code:

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

int main ( ) {
    char buff[BUFSIZ];
    FILE *fp = stdin;   // replace with fopen() call when you're ready
    while ( fgets( buff, sizeof buff, fp ) != NULL ) {
        int iHex;
        char sHex[20];
        if ( sscanf( buff, "%x", &iHex ) == 1 ) {
            printf( "As an int, we have %d\n", iHex );
        }
        if ( sscanf( buff, "%s", sHex ) == 1 ) {
            printf( "As a string, we have %s\n", sHex );
        }
    }
    return 0;
}

Perhaps something along the lines of a for loop and strlen(sHex) would be in order

To break the hex number up you could "mask" it by using the & operator and some bit shifting.

example:

Code:

hexNumber = 0xdab3;

nibble1 = (hexNumber & 0xF000) >> 12;
nibble2 = (hexNumber & 0x0F00) >> 8;
nibble3 = (hexNumber & 0x00F0) >> 4;
nibble4 = (hexNumber & 0x000F);

now nibble1 should contain "d" all by itself.
nibble2 should be a
nibble3 b
and nibble4 3

once youve broken them up you could do a loop and convert to binary like so

Code:

for(int loop = 8; loop >= 0; loop--) {
  int iBytes = (nibble1 >> loop) & 1;
  printf("%d", iBytes);
}

I am not promising that the info is 100% correct, but you should get the idea

Originally Posted by Vicious

Code:

for(int loop = 8; loop >= 0; loop--) {
  int iBytes = (nibble1 >> loop) & 1;
  std::cout << iBytes;
}

I am sure that works and all, but std::cout? This is the C forum.

lol, wooops, i'll edit that

guys that stuff looks really technical and i can't really understand it..
i'll definently spend alot of today trying to make something like you have suggested work, or possibly you could help me with this idea..

this is my current code.

Code:

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


FILE * inputdata;

void readfromfile(void);




int main()
{

	readfromfile();
	
	return (0);
}



void readfromfile(void)
{


	unsigned int hex;
	int i=0;

	inputdata = fopen("numbers.txt","r");

	printf("Line #	Hex		Decimal		Binary\n");

	
	while (fscanf(inputdata,"%x",&hex) == 1)
	{
	
	printf("%i	%8x	%u\n",i , hex , hex, hex);
	i++;

	}
}

and i realised that with this for loop i'm able to convert the numbers into binary like i need to, but i'm not able to work it into my printf. i couldn't figure out how.

Code:

for(i = 0; i < 32; i++)
printf("%d", (value >> (31 - i)) & 1);

i tried to put it inside the printf then i decided thats probably not even possible, then i was trying to work it into storing it into a new variable, but i just really couldn't grasp the concept of what was needed to acheive this. so if anyone could explain how i could use that to convert to binary that would be great. it does work, i just can't work it properly.