Final answer:
The missing category in the question is 'Processor state information,' which includes data like process register contents and program counter.
Step-by-step explanation:
The process control block information can be grouped into three general categories: Process identification, Processor state information, and process control information. The processor state information includes data such as the process's register contents, program counter, and scheduling information, which are essential for the system to pause a process and resume it later without loss of information.
Process identification typically includes a unique process ID and may also comprise of parent process ID and user ID related to the process. Lastly, process control information encompasses various attributes related to process scheduling, process state, priority, pointers to process queues, and other flags necessary for the management of the process within the operating system.
Process identification includes details such as process ID, parent process ID, and user ID. State information includes the current execution state of the process, such as the program counter value and register contents. Process control information includes details such as the priority of the process and the resources allocated to it.