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| | Commonly used signals include the Kill and the Wakeup codes. Wakeup is essential to let the next process in an I/O queue get its turn in line at a path or device. | | Commonly used signals include the Kill and the Wakeup codes. Wakeup is essential to let the next process in an I/O queue get its turn in line at a path or device. |
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| − | OS-9 has a signal-sending call, F$Send, which sends a one byte signal to the process ID specified, and causes the recipient to be inserted in the active process queue. Any signal other than Kill or Wake is put in the PSSignal byte of its process descriptor. | + | OS-9 has a signal-sending call, F$Send, which sends a one byte signal to the process ID specified, and causes the recipient to be inserted in the active process queue. Any signal other than Kill or Wake is put in the P$Signal byte of its process descriptor. |
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| − | If it was the Kill signal, the PSState byte in the process descriptor has the Condemned bit set to alert the kernal to kill that process. A Wake signal clears the PSSignal byte, since just making the destination an active process was enough. | + | If it was the Kill signal, the P$State byte in the process descriptor has the Condemned bit set to alert the Kernel to kill that process. A Wake signal clears the P$Signal byte, since just making the destination an active process was enough. |
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| − | Signals are not otherwise acted upon until the destination process returns to the User state. (It'd be unwise to bury a process in the midst of using the floppy drives, for instance.) However, drivers and the kernal may take note of any pending signals and alter their behavior accordingly. | + | Signals are not otherwise acted upon until the destination process returns to the User state. (It'd be unwise to bury a process in the midst of using the floppy drives, for instance.) However, drivers and the Kernel may take note of any pending signals and alter their behavior accordingly. |
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| − | When the kernal brings a process to the active state, the PSSignal byte in the descriptor is checked for a non-zero value (Kill=0, but the Condemned bit was set instead, causing a rerouting to the FSExit 'good-bye' call as soon as the killed process enters a non-system state). The process is given a chance to use the signal right off. | + | When the Kernel brings a process to the active state, the P$Signal byte in the descriptor is checked for a non-zero value (Kill=0, but the Condemned bit was set instead, causing a rerouting to the F$Exit 'good-bye' call as soon as the killed process enters a non-system state). The process is given a chance to use the signal right off. |
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Exception encountered, of type "Error"