This may be a fundamental misunderstanding worth expanding on.

To most programmers, "pause" means to relinquish the CPU for some amount of time. This is typically done by a sleep() call, which lets your program relinquish the CPU for multiples of 1 second, or by a select() call, which relinquishes the CPU for multiples of a millisecond.

By "relinquish" we mean "not run". The operating system won't schedule your program for execution until at least the specified period of time has elapsed. None of your program's instructions are executed. The CPU is then available for other processes.

Rather than relinquishing the processor, the script above runs in place, in a fairly tight loop, until it sees that the clock has reached the desired time. As you've noted, this isn't processor friendly, and probably isn't what you intended.