CPU Time

CPU time (or CPU usage, process time) is the amount of time for which a central processing unit (CPU) was used for processing instructions of a computer program, as opposed to, for example, waiting for input/output (I/O) operations.

The CPU time is often measured in clock ticks or seconds. CPU time is also mentioned as percentage of the CPU's capacity at any given time on multi-tasking environment. That helps in figuring out how a CPU’s computational power is being shared among multiple computer programs.

In contrast, elapsed real time (or simply real time, or wall clock time) is the time taken from the start of a computer program until the end as measured by an ordinary clock. Elapsed real time includes I/O time and all other types of waits incurred by the program.