Memory Management

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Contents
Question 1 2
Answer 1 2
Question 2 2
Answer 2 2
Question 3 2
Answer 3 2
Question 4 3
Answer 4 3
Question 5 3
Answer 5 3
Question 6 3
Answer 6 3
Inverted page table 4
Multilevel page table 5
Virtualized page table 5
Question 7 5
Answer 7 5
Question 8 6
Answer 8 6

I need help with the following problem.

Decribe in a few paragraphs
Question 1
Which of the following components is responsible for loading the initial value in the program counter for an application program before it starts running:
• Compiler
• Linker
• Loader
• Boot module or boot ROM
Answer 1
Loader

Question 2
Identify three styles of switching from user mode to supervisor mode.
Answer 2
1. Interrupts, when a device sends an interrupt to the CPU.
2. When a program executes a system call, which is usually implemented by a trap instruction.
3. When a program performs an operation that causes a hardware exception, such as divide by zero, illegal memory access or execution of an illegal opcode.

Question 3
Explain the steps that an operating system goes through when the CPU receives an interrupt.
Answer 3
• First, the hardware switches the machine to supervisor mode and causes control to transfer to a routine at a pre-specified address. The operating system has already loaded that address with a pointer to a function that handles the interrupt.
• The function starts by saving all registers, possibly setting the allowed interrupts to a level that guarantees correct execution of the operating system, and then executes the code to serve the interrupt.
• When the operating system is done, it restores the registers again and calls the "reti" to return to the user program that was running when the interrupt occurred.
• If there is no runnable program, the operating system jumps to the idle loop and waits for an interrupt.
• Finally, if the interrupt occurred while the operating system was running, then the OS simply restores the registers and jumps to the instruction following the
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