Question

I have already posted this before and I am looking at different answer. using C
outputs and comments will be appreciated.

QUESTION: Write a function to check if a machine uses little endian or big endian notation.The basic structure of the program is givenbelow.
You are expected to write the function checkEndianess(), complete the main function implementation to print the value returned by the function and print if the machine is “Little Endian” or “Big Endian”, compile and run the program. The function checkEndianess() should return the following values: •0if the architecture is "Little Endian" •1if the architecture is "Big Endian".

KEY POINTS:
1.Make sure to call the function name correctly (same function name as given in this document) in the main program.
2.Comment out all non-C statements.
3.Follow all instructions mentioned above.
We will check your function by calling the function in the following main function.
#include<stdio.h>
int main()
{int check; // Variable: "check" will hold the value returned by the function
//Call the function to check the Endianness here
// This is where your function will be called to return endianness
check = checkEndianess ();
// TODO for TAs and Students who will use this function to check the student function
// TODO Write the code to check the value returned by the function
// TODO print if the system uses little Endian or big Endian notation

return(0);
}
/* Function "checkEndianess" checks the Endianness of the machine on which this program is executed. The function should return 0 if the architecture is "Little Endian" and return 1 if the architecture is "Big Endian". */
int checkEndianess ()
{

}

Please note that if you implement the function checkEndianess in a separate file other than the file containing the main function, you need to declare this function as an extern in the file containing the main function.

Answer 1

#include <stdio.h>

int checkEndianess ();

int main(void) {
        int check;
        
        check = checkEndianess();
        
        if (check)
                printf("machine is big endian.\n");
        else
                printf("machine is little endian.\n");

}

int checkEndianess ()
{
        // Declaring a unsigned character pointer, because dereferencing 
        // the character pointer can give the value at particular memory 
        // without the signed notation.
        unsigned char *ptr;
        
        // variables to 
        int x, i, bigEndian;
        
        x = 0x12345678;
        
        // Get the address of the first byte of x.. int is 4 byte. &x makes ptr point to first byte only.
        ptr = (unsigned char *)&x;

        /*
        The Big Endian machine stores the Lowest byte of the numbers on the higher memory locations, and highest byte on the lower memory locations.. 
        So if 0x12345678 need to be stored in big endian machine starting from address 100, then 
        location 100 contains: 12
        location 101 contains: 34
        location 102 contains: 56
        location 103 contains: 78       
        */
        // x >> 24, Shifts the bytes to left side on user input integer. 
        // So we basically compare the value of first memory location with the 
        // value of left 8 bits of the x.
        // similarly for other bytes.
        
        bigEndian = (*ptr == (unsigned char)(0xff & (x >> 24))) &&
        (*(ptr + 1) == (unsigned char)(0xff & (x >> 16))) &&
        (*(ptr + 2) == (unsigned char)(0xff & (x >> 8))) &&
        (*(ptr + 3) == (unsigned char)(0xff & x));

        return bigEndian;
}

**************************************************

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