[iyonix-support] Re: Card Reader query
- From: Julie <julie@xxxxxxxxxxxxxxxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Sat, 19 Dec 2009 09:42:37 +0000 (GMT)
On 18 Dec, Iyonix PC Owner <iyonix@xxxxxxxxxxxxxx> wrote:
> On Fri, 18 Dec 2009, John wrote:
> Hi,
> > Can anyone tell me whether this is likely to work on the Iyonix, please?
> > http://www.amazon.co.uk/Integral-Single-Slot-SDHC-Reader/dp/B000VY80AM/ref=sr_1_1?ie=UTF8&s=electronics&qid=1261157271&sr=8-1
> > (when it eventually arrives) Should be Ok on my laptop, but would be useful
> > if there is a way of getting it to work on RO. One problem I forsee is that
> > it will have a 16gb card to read.....
> As far as I can recall from some programming exercise I did one year ago,
> RISC OS in gerneral, not just on the Iyonix, works with 32 bit registers.
> As nowadays C and it's derivatives are widely used as a programming
> language, the representation of a 32 bit register is an integer, which
> uses one of the 32 bits for the sign. (+/-) That leaves us with 31 bit,
> which can be used up to 2147483648 which is 2^30, or roughly 2 GB if you
> are counting bytes.
<snip>
It's been rather longer than a year since I did any C programming, but
IIRC, there is a choice of integer representations available. Both
signed and unsigned can be used, as well as 'short' and 'long' and
possibly 'double' (the exact length of these depends on the platform).
Unsigned long or unsigned double should give you the full 32 bits.
For example:
http://msdn.microsoft.com/en-us/library/7fh3a000.aspx
Julie
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