Using gettimeofday to compute reaction times

[reference to http://www.mac-forums.com/forums/os-x-darwin-development/38816-issue-using-times-function-intel-mac.html.]
I am (trying to) help my seventh-grade son with a project. He needs to record reaction time to at least millisecond precision. I have discovered that the time() function only reports to integer seconds precision, but it looks like gettimeofday() will do what I want. I am very inexperienced with C++ programming, however, so if it's not too much trouble, could someone post a sample code for me? Here's basically what I'm trying right now:

#include <iostream>
#include <time.h>
#include <sys/time.h>
using namespace std;

/* time example */

double time_inSeconds()
//define a function to return the time in decimal seconds
{
double seconds;
timeval t;
gettimeofday(&t,NULL);
seconds = t.tv_sec+t.tv_usec/1000000;
return seconds;
}

int main ()
{
double startTime, endTime, elapsedTime;
startTime=time_inSeconds();
printf("press return");
//stuff happens
getchar();
endTime=time_inSeconds();
elapsedTime=endTime-startTime;
cout << ("Elapsed time is ", elapsedTime);

return 0;
}
​

When I run this code, the printed output is an integer, not the decimal value that he needs.

Thanks.

So, you're trying to get us to do your son's homework for him?

deer dance said:

So, you're trying to get us to do your son's homework for him?

Click to expand...

Well, . . . not exactly. This piece makes life easier, but he can always revert to the stopwatch.

Does't that seemlike a logical idea?