Main Memory Part 1

Question 1

CPU is capable of directly accessing only CPU ______, _____ memory, and ________ memory

Answer 1

caches, main, persistent

Question 2

Programs must be loaded to ______ memory for execution

Answer 2

main

Question 3

Systems in the early days had _________ memory systems

Answer 3

physical

Question 4

In early days, the OS starts a physical address ____

Answer 4

zero

Question 5

In early days, application programs used the memory space not used by the ___

Answer 5

OS

Question 6

In early days, systems could only run _____ user program at a time

Answer 6

one

Question 7

Systems in the early days were _________ because of low _______ utilization

Answer 7

inefficient, resource

Question 8

In multi-programming, there needs to be ________ and ________ between processes

Answer 8

protection, isolation

Question 9

_______ ______can be used to protect and isolate processes in multi-programming

Answer 9

address space

Question 10

What is address space?

Answer 10

Easy-to-use abstraction of physical memory

Question 11

Address space provides an _______ that each process uses the whole memory space

Answer 11

illusion

Question 12

Address space _______ uses memory space

Answer 12

efficiently

Question 13

Each process has its own ______ _______ that starts from 0 and ends at max memory possible. This is called ______ ______

Answer 13

address space, virtual address

Question 14

Describe the 4 sections of the memory space from top to bottom.

Answer 14

Stack: Local vars and return addresses
Heap: Dynamically allocated
Data: Global vars
Text: Program code

Question 15

A ____ and a ______ register define the logical address space

Answer 15

base, limit

Question 16

Physical address = ______ + _________ _______

Answer 16

base, virtual address

Question 17

What is a base in the logical address schema?

Answer 17

Starting address in physical memory

Question 18

What is the virtual address in the logical address schema?

Answer 18

Offset into the address space

Question 19

The base and limit registers are supported by the __________ ___________ unit

Answer 19

memory management

Question 20

Modifying the base and limit registers requires __________ instructions

Answer 20

privileged

Question 21

_______ address space cannot be larger than _______ address space

Answer 21

logical, physical

Question 22

Logical address space must be stored __________

Answer 22

contiguously

Question 23

Logical address space may waste space between the ____ and ______

Answer 23

heap, stack

Question 24

A better alternative to logical address space would be __________

Answer 24

segmentation

Question 25

Segmentation generalizes _____ and_______

Answer 25

base, limit

Question 26

In a programmer's view of memory, a program is a collection of _______

Answer 26

segments

Question 27

In a prgorammer's view of memory, a segment is a logical unit such as...

Answer 27

* Main program * Functions, procedures * Method * Object * Local variables, global variables * Stack * Symbol tables * Arrays

Question 28

In segmentation, we have a base + limit pair per logical _______

Answer 28

segment

Question 29

In a segmentation architecture, what is the form of the logical address?

Answer 29

(segment-number, offset)

Question 30

A ______ table maps logical address to physical address

Answer 30

segment

Question 31

Each entry in the segment table has a ______, which is the starting physical address of segment, and a ______, which is the length of segment

Answer 31

base, limit

Question 32

One issue of segmentation is that the OS needs to _____ and __________ segment registers upon context switch

Answer 32

save, restore

Question 33

One issue of segmentation is managing _____ ______. The OS needs to find free space in memory for new address space

Answer 33

free spaces

Question 34

What is external fragmentation?

Answer 34

When physical memory becomes full of small holes of free spaces, making it harder to allocate new segments or grow existing ones.

Question 35

To fix the issues in segmentation, we use _____ _______ ___________ schemes

Answer 35

free space management