9.3.142 SYSTEM_CLOCK ([COUNT] [,COUNT_RATE] [,COUNT_MAX])

Description:  Returns integer data from a real- time clock.  
Class:  Subroutine 
Arguments:  There are three optional arguments[1]: 
COUNT (opt)  Must be scalar and of type default integer. It is set to a value based on the current value of the processor clock. The value is increased by one for each clock count until the value COUNT_MAX is reached, and is reset to zero at the next count. (COUNT lies in the range 0 to COUNT_MAX.) 
COUNT_RATE (opt)  Must be scalar and of type default integer. It is set to the number of processor clock counts per second.

If default integer is INTEGER(2), COUNT_RATE is 1000. If default integer is INTEGER(4), COUNT_RATE is 10000. If default integer is INTEGER(8), COUNT_RATE is 1000000.  

COUNT_MAX (opt)  Must be scalar and of type default integer. It is set to the maximum value that COUNT can have, HUGE(0)[2]. 

[1] All are INTENT(OUT) arguments. (See Section 5.10.)
[2] For more information on HUGE, see Section 9.3.54.

Examples

Consider the following reference:

CALL SYSTEM_CLOCK (COUNT=C, COUNT_RATE=R, COUNT_MAX=M)

If the default integer kind is INTEGER(4) and the internal counter was at zero 345 microseconds ago, the reference sets C = 345, R = 10000, and M = HUGE(0).

If the default integer kind is INTEGER(2) and the internal counter was at zero 345 milliseconds ago, the reference sets C = 345, R = 1000, and M = HUGE(0).


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