This document discusses endianness in computing. It defines endianness as the order in which bytes of a word are stored in computer memory. There are two types: little endian, where the least significant byte is stored first, and big endian, where the most significant byte is stored first. Intel processors use little endian format while Motorola processors use big endian. The document provides code samples to determine a processor's endianness and to convert between little and big endian formats.

2. A GENDA
 What is endian?
 The little endian
 The big endian
 Source code

3. E NDIAN ??
 Unit of data handled by a processor in a
particular architecture is called word. A word is
basically a fixed sized group of bits that are
handled as a unit by the instruction set and/or
hardware of the processor.
 The way a word is stored in memory by different
architecture is called endianness. There are two
methods two store a word in computer
memory, little endian and big endian.

4. L ITTLE E NDIAN
 In little endian based architecture little end (i.e. least
significant byte) of a word is stored first.
 Example: In a 32bit architecture a 32 bit hex word say
0xA6D85FBC is stored at base address 0xA2076F20. In
a little endian based architecture least significant byte
of word i.e. 0xBC is stored first and then next least
significant byte and so on..
 Base_address (0xA2076F20) : Data 0xBC
 Base_address+1(0xA2076F21) : Data 0x5F
 Base_address+2(0xA2076F22) : Data 0xD8
 Base_address+3(0xA2076F23) : Data 0xA6

5. B IG E NDIAN
 In big endian based architecture big end (i.e. most
significant byte) of a word is stored first.
 Example: In a 32bit architecture a 32 bit wide hex
word say 0xA6D85FBC is stored at base address
0xA2076F20. In a big endian based architecture most
significant byte of word i.e. 0xA6 is stored first then
next most significant byte and so on..
 Base_address (0xA2076F20) : Data 0xA6
 Base_address+1(0xA2076F21) : Data 0xD8
 Base_address+2(0xA2076F22) : Data 0x5F
 Base_address+3(0xA2076F23) : Data 0xBC

6. S OURCE C ODE
 Intel processors are little endian based while
Motorola processors are big endian based.
 Source code to determine weather your
processor is little or big endian is given below:
int main()
{
int iNum = 1;
if(*(char *)&iNum == 1)
{
printf("nLittle-Endiann");
}
else
{
printf("Big-Endiann");

7. S OURCE C ODE
 Source code to convert little endian to big
endian and vice-versa is given below
int ChangeEndianness(int num)
{
char byte0, byte1, byte2, byte3;
byte0 = (char)(num & 0x000000FF) >> 0 ;
byte1 = (char)(num & 0x0000FF00) >> 8 ;
byte2 = (char)(num & 0x00FF0000) >> 16 ;
byte3 = (char)(num & 0xFF000000) >> 24 ;
return (int)((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | (byte3
<< 0));
}

8. Q UESTIONS ?
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