Abstract: A multiprogramming/multiprocessing computer system for executing a plurality of processes sharing common information in the form of records, pages or messages, employing an apparatus for avoiding an interference between two processes seeking access to elements of common information. The system operates to store in a first memory utilization data in table form identifying the processes which have accessed each individual element of common information. A second memory stores a matrix of precedence data representing the relative order in which processes must access the common information in accordance with a predetermined set of access rules. When a first process enters a request to access an element of common information, the system identifies from the utilization table any other process which, according to the access rules, must be given precedence to the common information over the first process.

Abstract: A general mechanism and a family of hardware/firmware instructions are disclosed, which allow sharing files and resources without interference one from the other in a multiprogramming, multiprocessing environment. The basic inventive concept of interference is developed and several embodiments of the invention are disclosed. Protective mechanisms determine when sharing of files or resources is safe, and provide alternate courses of action to be taken by the computer system when it is determined that sharing would provide wrong results.