Two OS processes A and B reside within a single computer, along with its operating system. The memory occupied by A and B are each contiguous in main memory. A resides in physical addresses 0x100000 through 0x103FFF. B resides in physical addresses 0x200000 through 0x210FFF. The operating system resides in physical addresses 0x000000 through 0x0FFFFF. The Memory Management Unit uses Base and Limit registers.

If process A makes a read() system call that blocks, the operating system may run process B. Explain in detail the sequence of actions taken by the operating system to make this switch. Include changes to the program counter, stack pointer and other general purpose registers, process control register and process descriptor (or process control block).