Test if your machine is big or small endian
Compile .c file and run with compiler of your choice :)
Theory:
Consider the following value 0x12345678
Big endian stores the most significant bits (0x12) at the first memory address, giving the following format: 12(+0) 34(+1) 56(+2) 78(+3)
Little endian would be the opposite: 78(+0) 56(+1) 34(+2) 12(+3)
By loading the value 0x12345678 into memory on your machine, and grabbing the byte at offset +0 (exactly where the pointer is) should tell you whether or not your machine is big or small endian depending on its value :)