PowerAda 106
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(106) Implementation-defined aspects of delay_statements.
See D.9(8).
For delay statements that use the type DURATION defined in package ADA.CALENDAR any value that, when converted to type duration, results in a positive non-zero value will cause the task to block. DURATION'SMALL is about .0006 seconds.
For delay until statements that use the type TIME defined in ADA.REAL_TIME time is expressed in nano-seconds (10**-9). Any value that is non-zero causes a call to the underlying AIX support.
A value of zero causes the executing task to go to the end of the run queue for its priority.