29. A trap semaphore as recited in claim 28 including fifth means responsive to said second means for determining whether or not said second process is operating in the preferential mode.
28. A trap semaphore for interprocess communication and synchronization between a first and second process comprising: a. first means for detecting a trap-event occurrence, in a first process said trap event occurrences being the occurrence in a first process of a condition which is significant to a second process and which requires in response thereto preferential out-of-sequence processing by a preferential mode of said second process; b. second means for receiving message-notification on behalf of said second process of said trap event occurrence; c. third means responsive to said first means for providing said second means with message notification of said trap-event occurrence; and, d. fourth means responsive to said second means for trapping said second process upon notification of said second means of said trap-event occurrence.