RE: what is Hex?
- From: "Chris Hofstader" <chris.hofstader@xxxxxxxxxxx>
- To: <programmingblind@xxxxxxxxxxxxx>
- Date: Thu, 21 Feb 2008 06:48:48 -0500
Whoa! Another Coco programmer who admits to it!
-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Ian D. Nichols
Sent: Wednesday, February 20, 2008 11:00 PM
To: programmingblind@xxxxxxxxxxxxx
Subject: Re: what is Hex?
Hi Chris,
My point was that the leading zero is necessary only if the hex number
begins with a digit that is a letter (A - F). int 21h is fine, but int A0h
would have to be int 0A0h to avoid getting an error message.
I've been hit hard by nostalgia on this one, too. More than 20 years ago I
began by "compiling" my own little assembler programs on a Radio Shack Color
Computer by poking machine language codes into memory by hand. The effects
were sometimes quite interesting if I made a mistake in hexadecimal mental
arithmetic and poked in an incorrect offset value for a relative jump!
Ian
Ian D. Nichols,
Toronto, Canada
----- Original Message -----
From: "Chris Hofstader" <chris.hofstader@xxxxxxxxxxx>
To: <programmingblind@xxxxxxxxxxxxx>
Sent: Wednesday, February 20, 2008 5:12 PM
Subject: RE: what is Hex?
> I'm not sure that the leading zero is a requirement but I haven't used an
> assembler on Intel x86 much since the DOS days. I know that back in those
> days, I could use the instruction, "int 16h or, to make a DOS call, int
> 21h"
> without putting a leading zero ahead of the interrupt value. Of course,
> lots of the really useful interrupts 2 (single step), 3 (breakpoint) and 9
> (keyboard) look the same in hex or decimal so they wouldn't matter if they
> had leading zeroes or not. If I remember correctly, Wordperfect prior to
> v5
> for DOS had a hook for screen readers located at interrupt A0h but it has
> been an eternity since I looked at that while working on "Right Writer" a
> grammar checker for DOS.
>
> Alas, I grow more nostalgic as this thread grows...
>
> cdh
>
> -----Original Message-----
> From: programmingblind-bounce@xxxxxxxxxxxxx
> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Ian D. Nichols
> Sent: Wednesday, February 20, 2008 4:38 PM
> To: programmingblind@xxxxxxxxxxxxx
> Subject: Re: what is Hex?
>
> Hi,
>
> To add a little more to this topic, for the general inlightenment of those
> who don't already know:
>
> In Intel assembly language, a hexadecimal number must have an "h" at the
> end, an octal number must end with a "o", and a binary number with a "b".
> Without any of these, the assembler assumes the number is decinal.
> Further,
>
> a hexadecimal number that begins with any of the digits "a" to "F" must
> begin with a zero as well as ending with an "h", otherwise the assembler
> tries to interpret it as a label or variable.
>
>
> All the best,
>
> Ian
>
> Ian D. Nichols,
> Toronto, Canada
>
> ----- Original Message -----
> From: "Jamal Mazrui" <empower@xxxxxxxxx>
> To: <programmingblind@xxxxxxxxxxxxx>
> Sent: Wednesday, February 20, 2008 1:43 PM
> Subject: Re: what is Hex?
>
>
>> By the way, I think someone said that a hex number starts with 0. I
>> don't
>> think that's quite right. C derived languages typically distinguish a
>> hex
>> number with a preceding 0x, but the number is what follows the x. Other
>> languages or contexts use different conventions to distinguish hex from
>> decimal, e.g., Visual Basic uses a preceding &h sequence and Unicode uses
>> a preceding u. In other contexts, the number is understood to be hex, so
>> no additional prefix or suffix is needed.
>>
>> Here is a long Wikipedia article on hex
>> http://en.wikipedia.org/wiki/Hexadecimal
>>
>> Cheers,
>> Jamal
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