SHARED COMPUTER RESOURCE ALLOCATION SYSTEM HAVING APPARATUS FOR INFORMING A REQUESTING COMPUTER OF THE IDENTITY AND BUSY/IDLE STATUS OF SHARED RESOURCES BY COMMAND CODE

Computer system resources shared by several central processing units are allocated by allowing one processing unit to temporarily gain exclusive access to a particular shared resource. Access to a particular resource is controlled by a memory location which contains information representing the current state of the resource and the identity of any processing element currently utilizing the resource. In the case where several resources are interchangeable, the memory location may also contain information regarding the busy/idle states of other interchangeable resources. The memory location can be interrogated by any of the processing elements via command and address information. If the contents of the memory location indicate that the associated resource is not in use, then the interrogating processing element immediately obtains control of the resource. If the resource is in use, the identity of the processing element currently using the resource and any stored resource state information is returned to the interrogating processing element which can then continue processing without the resource or choose another idle resource.