How do you convert between little-endian and big-endian in code?
From NCERTAsked by Anonymous from Tokyo, Japan23 Oct 2026, 5:10 PM ISTUpdated
In one line
Little-endian and big-endian are two ways of storing multi-byte numbers, and you can convert between them by reversing the order of their bytes.
Endianness — Order of bytes in a computer word A diagram from Wikipedia showing how the bytes of a number are ordered in little-endian and big-endian formats. Image: Wikipedia
The rule
To convert a number from little-endian to big-endian (or vice versa), reverse the order of its bytes.
There is no single formula, but the process is: reversed_bytes = bytes[::-1] (in Python).
Let's understand it simply
Imagine you write the number 1234 on a piece of paper. In India, we write numbers left to right: 1-2-3-4. Computers also store numbers, but sometimes they start from the left (big-endian) and sometimes from the right (little-endian).
Think of a 4-digit number as 4 boxes. Big-endian puts the biggest part first (left), little-endian puts the smallest part first (right). To convert, you just flip the order of the boxes.
How it works
Take the number and break it into bytes (groups of 8 bits, usually 2 hex digits).
List the bytes in the order they are stored (little-endian or big-endian).
To convert, reverse the order of the bytes.
Put the reversed bytes back together to get the number in the new format.
How to convert between little-endian and big-endian
Break the number into bytes
Reverse the order of the bytes
Combine the bytes back into a number
The story behind it
The terms come from "Gulliver's Travels," where people argued about which end of an egg to break. In computers, different processors (like Intel and ARM) chose different ways to store numbers. This caused confusion when sharing data, so programmers needed a way to convert between them.
Where you see it in real life
Reading files from another computer: If a file was saved on a big-endian system but you open it on a little-endian PC, you must convert the bytes.
Networking: Internet protocols use big-endian, but many PCs use little-endian, so data must be swapped.
Microcontrollers: Some chips use little-endian, others use big-endian, so code must handle both.
Programming languages: Functions like htonl() and ntohl() in C convert between host and network byte order.
Hex editors: When you view binary data, you may need to swap bytes to read numbers correctly.
Why it matters
Data sharing: Without conversion, numbers can be misread, leading to bugs.
Cross-platform code: Software that runs on different hardware must handle both formats.
Exams and interviews: Understanding endianness is a common computer science question.
Debugging: Helps you spot and fix data corruption issues.
Worked example
Let's convert the 32-bit hexadecimal number 0x12345678 from little-endian to big-endian.
Given: 0x12345678 (in hex)
Step 1: Break into bytes: 12 34 56 78
Step 2: Little-endian order: 78 56 34 12
Step 3: To convert to big-endian, reverse: 12 34 56 78
Step 4: So, big-endian is: 0x12345678; little-endian is: 0x78563412
Common mistakes
Mixing up bits and bytes: Only bytes are reversed, not the bits inside a byte.
Forgetting the number of bytes: Always check if your number is 2, 4, or 8 bytes long.
Not converting when sending data between different systems: This can cause wrong values.
Remember it
Endian = "end in"; little-endian starts with the little end, big-endian starts with the big end. To convert, just reverse the bytes!
Check yourself
If a 2-byte number is 0x1234 in big-endian, what is it in little-endian?
0x3412, because the bytes are swapped.
Why do we need to convert between endianness when sending data over the internet?
Because different computers may use different formats, and the internet uses big-endian.
What is a common mistake when converting endianness?
Reversing bits inside a byte instead of just reversing the bytes.
Quick recap
Little-endian and big-endian are two ways to store multi-byte numbers.
To convert, reverse the order of the bytes.
Only bytes are reversed, not the bits inside each byte.
This is important when sharing data between different computer systems.
Functions like `htonl()` in C help convert between formats.
