Different computers and operating systems vary wildly in how they keep track of processor time. It's common for the internal processor clock to have a resolution somewhere between hundredths and millionths of a second.

As such its possible that the time to open a file is faster that what clock measures.

To get a better average I suggest: [list:0507a6cee9]

• create 100 files (perhaps write a program to do this)
• take a time measurement with clock()
• open all 100 files (I think you can do this, so Op have a limit on the number of file handles you can have open)
• take final time measurement.
• calculate time and output.

[/list:u:0507a6cee9] I would then place all of the above in a larger loop and repeat 3 to 5 times to see what the influence of the system cache is. The disk cache and system cache could cause large differences in your times.

If you can't open that many files all at once, then you might like to open, then close each one - though that now will give you a time for two operations.

Anyways, thats my two pennies worth. Good luck and please post back the results.

Either way, I would expect the fopen/fclose (or whatever you're using) to be quick, since its merely checking for the existance of the file.