Understanding Endianness

What is Endianness?

Endianness refers to the order in which bytes are arranged when representing multi-byte data types, such as integers or addresses, in their binary or hexadecimal form within a computer system. The two main types are:

• Big Endian: Most significant byte first.
• Little Endian: Least significant byte first.

The most significant byte is the one with the highest value, typically corresponding to the largest place value in a number. Conversely, the least significant byte is the one with the smallest value, often corresponding to the smallest place value, like the 1s position in a number.

Most modern computer architectures, like x86 and ARM, use Little Endian format.

Why Does Endianness Matter?

Endianness affects how data is stored, transmitted, and interpreted by different systems. When data is exchanged between systems with different endianness, it needs to be converted to avoid misinterpretation. In the context of Bitcoin, understanding endianness is important for correctly interpreting transaction data and addresses.

Big Endian Explained

In Big Endian representation, the most significant byte (the "big end") comes first. This order is often called the "natural" order because it matches how we typically write numbers.

Example: If we store the number 0x12345678 in Big Endian format, it is stored as:

Little Endian Explained

In Little Endian representation, the least significant byte (the "little end") comes first. This format is used by most modern computer architectures, such as x86 and ARM.

Example: The same number 0x12345678 in Little Endian format would be stored as: