Bitfields

Bitfields

[Jagadeesh Bhaskar P]

Hi all,
	What is a bitfield? How is it used in C??

TIA

-- 
With regards,

Jagadeesh Bhaskar P

Re: Bitfields

[Ronaldo Zacarias Afonso]

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  Hi Jagadeesh, 

  "bit field" is a way that let you define a varible to be less than a byte 
in size. For example: 3 bits. 
  It is used as structs. 

struct nibble { 
     unsigned int n0: 4; 
     unsigned int n1: 4; 
     unsigned int n2: 4; 
     unsigned int n3: 4; 
}; 

  In this way you have declared four variables, each with a size of four 
bits. 





>Hi all, 
> What is a bitfield? How is it used in C?? 
> 
>TIA 
> 
>-- 
>With regards, 
> 
>Jagadeesh Bhaskar P 
> 
>- 
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Re: Bitfields

[HIToC]

On Wednesday 01 December 2004 05:25, Jagadeesh Bhaskar P wrote:
> Hi all,
> 	What is a bitfield? How is it used in C??
>
> TIA


It is possible to use several of bit variables like fields within a struct.
You have to indicate first the name of the field, then the number of bits
that the field occupies. Also you have to put double points ":" between
the filed's name and its bit-size.
For example, you want to save the current date; you can define a
struct Date (YYYY/MM/DD) like this

struct Date {                              // Date format: YYYY/MM/DD
	unsigned	year    : 7;         // 0-127 (2000-2127)   [7 bits size]
	unsigned	month  : 4;		// 1-12                       [4 bits size]
	unsigned	day      : 5;        // 1-31                       [5 bits size]
};

In this case we have the complete date in a 16 bit variable (7+4+5=16 bit)!

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				HIToC 
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