Do you have a main() function?
Do you have a main() function? All C++ programs need main().
...I don't know where to enter the seconds...
Then, to call your sleep_seconds() function for 100 seconds, you would put this in main():
Actually, you can call your sleep_seconds() function from any other function. You don't have to call it from main().... But, let's assume that your program isn't that complicated. :)
It's just better paractice.
It's more portable. On some systems, CLOCKS_PER_SECOND may not be 1000.
So, it's just a good habit to make all your programs as standard and portable as possible.
On most systems, the execuitable is going to be the same using 1000, or CLOCKS_PER_SECOND. So, the final program won't be "better". But the source code will be more standardized.