Exam 1 Review

Base - CPU register

Holds the absolute address in memory of where the process space begins

Program Counter - CPU register

Holds the relative address of the next instruction

Instruction Register - CPU register

Holds the current instruction that is being executed

Accumulator - CPU register

Temporary storage that holds the result of an instruction

Memory Address Register (MAR) - CPU register

: Holds the address where data is to be read from or written to

Memory Buffer Register (MBR) - CPU register

Holds the data that is to be read/written in memory

User Registers (URX) - CPU register

Permanent storage that persists between cycles, is faster than main memory
■ UR0: User Register 0
■ UR1: User Register 1
■ etc.

I/O Address Register (IOAR) - CPU register

Holds the memory address used to communicate with external device

I/O Buffer Register (IOBR) - CPU register

Holds data to be read from or written to for an external device

logical address

the pc alone gives us this

physical address

the base + pc gives us this

program

is an executable file which gives instructions to an operating system.

only occupies space on a disk

process

s is an instance of a program which is active in the system.

requires more resources than just disk space

has its instructions and its data stored in the main memor

Explain the benefits of running programs concurrently

To reduce process latency:
- Running multiple processes \____________ where the cpu constantly switches between processes that are stored in the cache

The OS performs a context switch when it swaps out one active process for another

When a process is swapped out during a context switch, information about its state is stored in a process control block

The process control blocks are stored in a process table.

The size of the process table gives us the degree of \______________, or the degree of multiprogramming for an OS

Explain why having multiple cores on a CPU is helpful.

You are able to increase concurrency and running two programs in one clock cycle

How many bits are in a byte?

8

How many distinct addresses can be represented with 32 bits?

2^32

if maximum address: (2^32)-1

Explain what happens when an interrupt occurs.

The interrupt is processed immediately as soon as they happen. Also, control is handled to the OS, and the OS decides how the interrupt is utilized.

What is the purpose of the Process Control Block (PCB)?

Used to handle processes only, and nothing else.

When a process is swapped out during a context switch, information about its state is stored in a \_____ \_____ \__________

When is control given to an operating system's kernel code

To activate kernel mode, a trap instruction is executed by invoking a system call. This transfers control from the user program to specially protected kernel code which cannot be modified by users.

Can a child process modify the memory of the parent process?

No, a child and parent process are stored into two different memory spaces

A child thread can modify a parent thread because they are in the same memory space

List these items in order of which is fastest to access by the CPU:
• L2 Cache
• CPU Registers
• Disk Memory
• L1 Cache
• L3 Cache
• Main Memory

CPU registers
L1
L2
L3
Main memory
disk memory