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Show 94 v r Input/Output Conventions I/O Devices I/O in FLEX does not require an^ special statements; it is handled as a generalization of the assignment statement. How is this realized m actuality? Each device has a reserved variable name associated with it and, hence, there also exists a slot in a process stack somewhere in the system that is also associated with this name. This process stack is the I/O process stack and is pointed to by the "1/0" event request in the real-time sectior ot the process control que. v re 1 a1 1 \1 HI 1 I/O event | que I/O Control 'tape 3' 'tape 2' .' tape 1' 'tape 0' DR1 DR2 DR3 'printer DD 'printer !ß_ ' punch ' : f5 Line Going Out ... ^^ ^S 15 1 '^'.M ds' !D£l2/2 \^ l/O process stack x b Card Coming In... An I/O interrupt uses the number of the device that caused it as an index into the I/O process stack. In the |
