Data Transmission

Code

#include <stdio.h>
#include <stdint.h>

void convert_to_big_endian(uint32_t value, uint8_t arr[4]) 
{
    arr[0] = (uint8_t)(value >> 24);
    arr[1] = (uint8_t)(value >> 16);
    arr[2] = (uint8_t)(value >> 8);
    arr[3] = (uint8_t)(value);
}

int main() 
{
    uint32_t value;
    uint8_t arr[4];
    scanf("%u", &value);
    convert_to_big_endian(value, arr);
    for (int i = 0; i < 4; i++) 
    {
        printf("%u", arr[i]);
        if(i<3)
        {
            printf(" ");
        }
    }
    return 0;
}

Solving Approach

This code is a utility for Endianness Conversion. Specifically, it takes a single 32-bit integer (which is usually stored in a single "block" in memory) and breaks it down into 4 individual bytes ordered in Big Endian format.

1. What is Big Endian?

"Big Endian" means the Big End (the most significant part of the number) is stored at the first memory address (index 0).

In many modern computers (like those using Intel or AMD processors), numbers are stored in "Little Endian" format (backward). However, Network Protocols and Automotive UDS/CAN standards almost always require Big Endian. This code acts as the "translator" to prepare data for transmission over a network or vehicle bus.

2. The Extraction Logic

To break the 32-bit number into 4 bytes, the code uses a "Shift and Chop" method:

• value >> 24: Moves the highest 8 bits all the way to the right.
• value >> 16: Moves the second-highest 8 bits to the right.
• value >> 8: Moves the third-highest 8 bits to the right.
• (uint8_t) Casting: This "chops" off everything except the last 8 bits, effectively isolating one byte at a time.

3. Step-by-Step Example

Suppose we have the Hexadecimal value 0x12345678 (Decimal: 305419896).

Final Byte Array: [18, 52, 86, 120]

4. Key Takeaways for Others

• Portability: This code is "Endian-neutral." Regardless of whether your computer is Little Endian or Big Endian, this math will always produce a Big Endian array.
• Network Byte Order: In networking, Big Endian is referred to as "Network Byte Order." If you are writing code for sockets or Ethernet communication, you will use this logic constantly.
• Memory Management: The function takes uint8_t arr[4] as a parameter. In C, this passes a pointer to the array, meaning the function modifies the original array created in main().