[oclug] What is this (C question)

[Gilles J. Seguin]

Jon Earle wrote:
> 
> Given a variable declaration of the form:
> 
> unsigned int index:10
> 
> What is the ':10' for? I saw this as part of a struct containing 3 or so
> such entries.

Bit fields

It can be used to pack data into bits and give each of those 
bits a name as a member of a structure.

But you cannot fetch their address(using &), and you cannot
create pointer to them,  Other then these two restrictions,
they are handled in the same way as ordinary variables.
You are choosing space over speed.
The compiler produces the code to properly insert
and extract them at the expense of speed.