RE: [Dev-C++] new is a wrapper around malloc so...

[Per W. <pw...@ia...>]

A 32-bit pionter is an unsigned entity, so it can span 2^32 bytes - 4GB.
From this address space, the different OS then reserves areas for OS code,
buffers, IPC etc. Depending on OS, you may normally not allocate more than
2 or 3GB for a single application.

This is the big reason why the world is so desperately wanting 64-bit
machines. In database solutions it is quite common to memory-map the
database files. However, 2-3GB is a puny database.

/Per W

On Wed, 16 Jul 2003, Daniel Glenfield wrote:

> All I know is that the MSDN documentation I read says 2GB. I'm not sure
> about how you calculate it all, so you're one up on me!
>
>
> >From: "Abhijit Shylanath" <mu...@gm...>
> >To: "Daniel Glenfield" <sp...@ho...>
> >CC: "Dev-Cpp mailing list" <dev...@li...>
> >Subject: RE: [Dev-C++] new is a wrapper around malloc so...
> >Date: Wed, 16 Jul 2003 00:40:19 +0530
> >
> >
> > > In 16 bit your code is separated into 'segments' each a maximum of 64k
> >in
> > > size. 32-bit can have up to 2GB segments (!!!).
> >
> >4G, right? (2^32).
> >
> >However, that's true only on a 32-bit system (as you've said)... what
> >platform are you building on? On 16-bit (`real-mode') DOS, even though
> >sizeof(farptr) will give you four, it cannot address 32-bits worth of
> >memory. Far pointers work like this:
> >
> >	32 bits of farptr  =
> >	16 bits of segment .
> >	16 bits of offset
> >
> >The effective address is actually calculated by multiplying the segment by
> >16 decimal (0x10 (which is equivalent to left-shifting by four)) and then
> >ADDING the offset... so that if your far-ptr has this value:
> >
> >	0x1234abcd
> >
> >Written as:
> >
> >	1234:abcd
> >
> >Its effective address, which is worth 20-bits (and can therefore address
> >2^20 = 1M) is calculated  as:
> >
> >	0x12340
> >+	 0xabcd
> >-------------
> >=	0x1cf0d
> >
> >Whereas, in the flat memory model(protected-mode), the effective address
> >would itself be
> >
> >	0x1234abcd
> >
> >--
> >Abhijit Shylanath
> >Homepage: http://mudeth.tripod.com/
> >
>
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