Lecture 4

Question 1

Virtual memory

Answer 1

Virtual memory consists of a large set of memory address references

Question 2

Words

Answer 2

fixed-sized data-chunks used by the CPU for

physical memory assignment.

Question 3

Virtual memory motivation

Answer 3

amount of memory required
to run all processes on any modern OS invariably exceeds the amount of physical
(main) memory available.

Question 4

Memory management

Answer 4

Multiple processes in memory at once, sharing physical memory addresses and protected from each other.

Question 5

Physical memory address conflict

Answer 5

when two virtual memory addresses translate to the
same physical address. an address conflict resolution check is needed before a new process can be swapped in from virtual memory

Question 6

Which part of the computer solves address conflict?

Answer 6

MMU (Memory management unit)

Question 7

What is a program in the context of an OS?

Answer 7

source code, libraries and data necessary

to run the program

Question 8

Process

Answer 8

a process is the program executable (.exe) actually

running

Question 9

Executable

Answer 9

An executable (exe) is thus a process that has been scheduled to run by the OS and
is currently suspended (stored in virtual memory) or is currently running (stored
in main memory).

Question 10

dynamic linking

Answer 10

deferring the resolution of some undefined symbols until a program is run

Question 11

Static linking

Answer 11

linking of libraries to be used by a given program

may be done at compile-time

Question 12

Linker

Answer 12

a linker or link editor is a programming language utility
program that takes one or more object files generated by a compiler and combines
them into a single executable file, library file, or another object file.

Question 13

Page replacement algorithm

Answer 13

A page-replacement algorithm decides what memory chunks (pages) to swap-into
main memory (and out of virtual memory), and thus what processes (i.e. split into
pages) should be running in main memory at any given time.

Question 14

Kernal part of any process

Answer 14

The kernel part of any process
contains addresses of OS-specific libraries and other data that must be executed in
order for the process to run at all

Question 15

Uni programming

Answer 15

only one process runs at a time and a process always runs at same
place in physical memory, but a process can access any physical memory address. There is no translation or protection.

Question 16

Why is uni programming infeasible?

Answer 16

Modern programming applications are too complex.

Question 17

Original concept of Multi programming

Answer 17

Each process
(application) was allocated a specific address in main (physical) memory, but there
was still no memory address translation or protection. In this case, the linker and
loader dynamically adjusted program addresses when they were loaded to try and
prevent overlap of processes concurrently loaded into main memory.

Question 18

Later version multiprogramming

Answer 18

The two special registers: BaseAddr and LimitAddr prevented users from straying
outside their designated memory areas when running processes. Thus, if a user
tried to access an illegal address, this caused an error and the process would not
try to execute. Users could not change the base/limit registers.