Week 11

Question 1

Name the three types of shared memory architectures

Answer 1

Database centric

blackboard

Rule-based

Question 2

Describe database centric memory architectures

Answer 2

Coordination is achieved through a database for shared data, typically asynchronously

Question 3

Describe a blackboard type shared memory architecture

Answer 3

Concurrent tasks or agents synchronously update a common memory data storage (the blackboard) and react to changes on the blackboard made by other agents.

Question 4

Describe a rule based shared memory architecture?

Answer 4

Rules stored with the data in a common area to be applied or queried

Question 5

What are the three types of messaging architectures?

Answer 5

Event-driven
Publish-subscribe
Asynchronous message

Question 6

What is event-driven messaging architecture?

Answer 6

An underlying system has a list of functions to invoke each time that a particular event happens

State machine

MVC for user interfaces

Question 7

What is a publish-subscribe messaging architecture?

Answer 7

Agents can ask to hear about particular event (subscribing)

Agents that compute results or identify changes can choose to let other agents know about the change (publishing)

Question 8

What is an asynchronous message type messaging architecture?

Answer 8

Program components maintain mailboxes in which other parts of the programs can send messages to be read when convenient to the receiever.

Question 9

What are the two adaptable systems?

Answer 9

Plug-ins/modular

Microkernal

Question 10

Describe a plugin/modular adaptable system?

Answer 10

A running program can have a new pieces added to it on the fly as needed

Question 11

Describe a microkernal adaptable system?

Answer 11

The core of the application (the kernal) is kept as small and as efficient as possible with all other elements added with restricted privileges.

Question 12

What are the four types of distributed system architectures?

Answer 12

Client-server (2 or 3 tier)

Peer-to-peer

Representational state transfer (REST)

Service-oriented (precursor to cloud systems)

Question 13

All printable characters in the ASCII table has a high-order bit of:

Answer 13

0

Question 14

If we don’t store the first 0 of each ascii byte, we can shrink the size of the files by how much?

Answer 14

12.5% (1/8)

Question 15

Bit operations are:

Answer 15

~bitwise complement

&bitwise and

Question 16

What are bit operations typical for?

Answer 16

masking

Question 17

How do we use a bitewise complement?

Answer 17

Switch 0 to 1 in binary representation.

Question 18

How do we use a bitwise and?

Answer 18

Bit remains 1 when both numbers have a 1 in the same spot

Question 19

Bitwise or

Answer 19

Bit remains 1 when either number has a 1 in a position

Question 20

Bitwise exclusive or

Answer 20

Bit becomes 1 when exactly one of the two numbers has a 1 in the position

Question 21

What is bit masking?

Answer 21

THe process of selecting specific bits from a binary representation

Question 22

What are the typical uses of bit masking?

Answer 22

Combine lots of options into one integer (give each option its own bit)

Networking (identify subnets from IP addresses)

Question 23

How do we change permissions?

Answer 23

Chmod

Question 24

Unix stores all the permissions in a 16 bit word, 1 byte for each class of people.

Answer 24

Each bute has one bit for each permission type: 4==read
2==write
1==execute

Question 25

How are default permissions get set?

Answer 25

Using a mask. Accessed and set by the unmask command