Thread: about hexa-decimal numbers

hello all.

i have this problem. i have a file that is full of numbers, i want
to take these numbers (two at a time) and treat them as
hexadecimal.

for example, a file that contains the numbers

534545245237

i want to make that :

0x53 0x45 0x45 0x24 0x52 0x37

and i want to check the bits of them one by one :

0x53 : 01010011 // ((if bit0==1){dothat();} if(bit2==0){donot();}

etc...

is there a way?

thanks a lot.

read through one character at a time. the ones column will be added to the other column times 16. ie:
54 = 4 + (5 * 16)
more technically
54 = (4 * 16^0) + (5 * 16^1)

by now you should have a hex number you want to test for bits. 1 looks like this:

Code:

0000 0001

if you want to test the ones digit here you want to mask away all the unnecessary digits. 0x54 looks like this:

Code:

0101 0100

to test a bit you want to logical and it. in c, it's this sign: &

Code:

0101 0100
&
0000 0001
=
0000 0000

and returns a one only when both are ones.
you want to set up this kind of loop:

Code:

int x = 0x57;
for (int i=0x80;i;i>>=1)
  if (x & i)
    printf("1");
  else
    printf("0");

the i>>=1 shifts i's bit once to the right.
i starts off as

Code:

1000 0000
0100 0000
0010 0000
0001 0000
0000 1000
0000 0100
0000 0010
0000 0001

every time you test the other number to see if the bit is set, then do something accordingly.

hello and thanks for the answers,

ygfperson, in order to make the characters numbers, i must
use the atoi function. but what will happen if i have letters?
e.g. 0x5a?

thanks.