OCCUPATION CONTROLLER OF INPUT AND OUTPUT DEVICE

PURPOSE:To prevent double registration by transferring the occupying right by adding +1 to contents of a pointer A to make scanning of a queuing processor unnecessary and adding +1 to contents of a pointer B just after the registration of an occupation request. CONSTITUTION:An occupation queue management table is set in a memory 119. Addresses of control circuits 111 and 112 are defined as A and B respectively. A processor 101 writes data 1101 in the address B. The control circuit 112 turns on a gate 118 to transfer the address indicated by a pointer 116 to the memory 119 and registers data 1101 to the memory 119 through a data line 129. After registration is terminated, a signal line 123 is set to ''1'' to write contents of an incrementer 114 in the pointer 116. When a processor 102 reads the address A, the control circuit 111 turns on a gate 117 to transfer the address in a pointer 115 to the memory 119 and reads contents of the memory 119 through a data line 129 and sends table contents to the processor 102 through a common bus 104. Thus, queue management is performed to prevent double registration.