Abstract: 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.

Abstract: Method and apparatus for automatically controlling aerial photographic cameras. An exact and reliable control device of low electronic and optical cost, which unburdens the operator, is realized by means of two photoreceiver lines positioned parallel to each other and perpendicular to the flight direction. At least the first line is connected to a data memory, which as well as the second line is connected to a correlator. The correlator is connected, via units for calculating the vg/hg ratio and/or the drift, to setting mechanisms of the aerial camera. A third photoreceiver line can also be provided, coupled subsequently to a data memory. The invention is utilizable in photogrammetry.