Thread: what is the relation between low– high part and the QuadPart in a UlargeInteger?

Hello Guys,
I work with windows 10 and VisualStudio; I should transform window FileTime in Unix time (Epoch time); I found the formula to convert the number of seconds in the windows FileTime to number of seconds in the Unix time: Unix time = (windows FileTime/10000000) - 11644473600.
In order to work with the window file time structure I have to “copy the low- and high-order parts of the file time to a ULARGE_INTEGER structure, perform 64-bit arithmetic on the QuadPart member” (from Microsoft doc).

What is not clear to me and I would like to ask you is: what is the relation bewtween low – high parts and the QuadPart? If I print these three numbers (see code below), I do not see the relation.
Here we have the code:

Code:

#include <stdio.h>
#include <windows.h>

int main()
{

ULARGE INTEGER U;
FILETIME T;

  GetSystemTimeAsFileTime(&T);
  U.LowPart=T.dwLowDateTime;
  U.HighPart=T.dwHighDateTime;
  printf(“Windows FileTime, QuadPart: %llu \n HighPart: %lu \n LowPart: %lu \n”, U.QuadPart, U.HighPart, U.LowPart);

//Unix time calculation:

  U.QuadPart = U.QuadPart/10000000 – 11644473600;
  printf(“Unix Time: %llu \n”, U.QuadPart);
  return 1;
}

Thank you for your help
Kind regards

Dear Salem,
thank you for your explanation
kind regards
Alberto