Any Unix kernel keeps track of how much CPU activity is being carried on by the system. These statistics are used by various administration utilities such as top. A user who enters the uptime command sees the statistics as the "load average" relative to the last minute, the last 5 minutes, and the last 15 minutes. On a uniprocessor system, a value of 0 means that there are no active processes (besides the swapper process 0) to run, while a value of 1 means that the CPU is 100 percent busy with a single process, and values greater than 1
mean that the CPU is shared among several active processes. 
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