[Tutor] A file containing a string of 1 billion random digits.

Dave Angel davea at ieee.org
Mon Jul 19 04:26:36 CEST 2010

Steven D'Aprano wrote:
> On Sun, 18 Jul 2010 08:30:05 pm Richard D. Moores wrote:
> <snip>
> What do you mean, "couldn't handle"? Couldn't handle 800 million of 
> what? Obviously not bytes, because your laptop *can* handle well over 
> 800 million bytes. It has 4GB of memory, after all :)
> <snip>

> This is just an example, of course. As they say, the devil is in the 
> details.
>>>> Memory usage went to 80% (from
>>>> the usual 35%), but no higher except at first, when I saw 98% for
>>>> a few seconds, and then a drop to 78-80% where it stayed.
>>> That suggests to me that your PC probably has 2GB of RAM. Am I
>>> close?
>> No. 4GB.
> Interesting. Presumably the rest of the memory is being used by the 
> operating system and other running applications and background 
> processes.

The amount of physical RAM has little to do with the size that an 
application can reach.  An application is limited by several things, but 
physical RAM mostly has an effect on performance, not on the size of the 

It is limited by the size of the swap file, and by how much of that swap 
file is in use by other apps, and by the system.  And a 32bit app is 
limited by the 4gb (virtual) address space, even if you have 8gb of 
physical RAM.  And that virtual space is shared with various pieces of 
OS, with device driver space, and sometimes with some physical hardware 
that's memory mapped.

But you can run a 2gb app in 1 gig of physical RAM.  That's what the 
swap file is for.


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