Image:Endianessmap.jpg

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1 Explanation
- 1.1 Big
- 1.2 Little
2 Licensing

[edit] Explanation

This article describes how to apply the diagram Endianessmap.jpg that is shown and cited in Endianness and moved here for clarification.

Here is an example:

[edit] Big

In Big-Endian: Say you would want to:

write "0x12345678" 32 bit into memory at addr "0"
read back 16 bit from address "2"

You would take the parts of the diagram for 32 bit and Big-Endian:

 Value in register:
 12345678
  A B C D

 Register:
 |------->
  A B C D  32 bit access

 Memory:
 | A B C D  32 bit access address 0
 ---------
   0 1 2 3
   ^
   |-> map 0 here
   A B C D

 Result in memory: 
 | 12345678  
 ---------
   0 1 2 3

Now you would want to read back 16 bit from address "2" in Big-Endian: Then you would use:

 Value in memory: 
 | 12345678  
 ---------
   0 1 2 3

 Memory:
 | A B C D  16 bit access 2
 ---------
   0 1 2 3
       ^
       |-> map 2 here
       |--->
       C D  

 Register:
    |-->|
 A B C D  16 bit access

 Result in register: 
 | 00005678  
 ---------
   0 1 2 3

[edit] Little

In Little-Endian: Say you would want to :

write your "0x12345678" 32 bit into memory at addr "0"
read back 16 bit from address "2"

You would take the parts of the diagram for 32 bit and Little-Endian:

 Value in register:
 12345678
  A B C D

 Register:
  A B C D  32 bit access
 <-------

 Memory:
  A B C D |  32 bit access 0
 ---------
  3 2 1 0
        ^
      <-| map 0 here
  A B C D

 Result in memory: 
  12345678|  
 ---------
   3 2 1 0

Now you would want to read back 16 bit from address "2" in Little-Endian: Then you would use:

 Value in memory: 
  12345678 |
 -----------
   3 2 1 0

 Memory:
  A B C D |  32 bit access address 2
 ---------
  3 2 1 0
    ^
  <-| map 2 here
  C D  

 Register:
 A B C D  16 bit access
    |<--|

 Result in register: 
  00001234  
 ---------
   3 2 1 0

[edit] Licensing

I, the copyright holder of this work, hereby publish it under the following licenses:

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

This file is licensed under the Creative Commons Attribution-ShareAlike license versions 2.5, 2.0, and 1.0.

You may select the license of your choice.

A vector version of this image is also available, and should be used in place of this raster image whenever possible.
Note: this file will not be deleted for this reason, unless it is explicitly nominated for deletion. Deleting this image might break the “attribution path” for the new SVG image, which breaks licenses such as the GFDL.

Image:Endianessmap.jpg