operation system chapter 3

3.3 Original versions of Apple's mobile iOS operating system provided no means of concurrent processing. Discuss three major complications that
concurrent processing adds to an operating system.

1. The OS has to keep track of the main memory address space allocated to each process so that a process does not affect or harm other processes data. This is a necessary , for example, a virus may try to destroy or modify other process data.
2. Switching from one process to another process leads to time overhead(时间开销), this requires storing the current register values and loading the register values of the next process from its PCB(program Control Block).
3. If a running process requires large space in memory then other process needs to be dumped back to hard disk which again leads to time overhead.