Assignment 3

1. Give the following 3 database tables

Catalog Table

Circulation Table

Patron Table

To look for last name of the person who borrowed the book "Cost of freedom", which table(s) do I need to look up? Do I need to join tables? If yes, show the resultant table.

Ans:

Need to look up Catalog Table, Circulation Table and the Patron Table.

Yes, these tables need to be joint.

resultant table

2. What's the definition of Computer Networks?

Ans:

connecting more than 1 computers together for sharing resources using communication equipments

3. What are the 3 most basic communication components?

Ans:

a sending device

a receiving device

communication link

4. What is the name of the process which converts digital signal into analog signal? What is the name of the process which converts analog signal into digital signal? Why are these processes necessary for transmitting computer data via conventional phone lines?

Ans:

Converting digital signal into analog signal: Modulation

Converting analog signal into digital signal: Demodulation

These processes are necessary since only analog signal can be transmitted via phone lines (while data are represented in digital formats in computers.)

5. Does cable Internet service provide fixed transmission rate? If no, give one factor of the transmission rate.

Ans:

No, the transmission rate depends on the number of subscribers using the service in an area.

6. Give the definition of the following 3 types of transmissions. Also, give an example for each of them.

• simplex transmission
• half-duplex transmission
• full-duplex transmission

Ans:

simplex transmission:

single direction of data transmission

eg: radio

half-duplex transmission:

bi-directional data transmission but not simultaneously

eg: walki-talki

full-duplex transmission:

sending and receiving data at the same time (simultaneous bi-directional data transmission

eg: telephone

7. Give the definition of Bandwidth.

Ans:

range of frequency that a communication medium can carry

8. Under the Ethernet protocol, does a computer send out data while someone else is sending out data? When a collision occurs, the data being transmitted is destroyed. What will the senders do after the collision?

Ans:

No, a computer doesn't send out data while someone else is sending out data.

When a collision occurs, both senders wait for a random amount of time and try to resend again.

9. State 1 problem of the token ring network protocol.

Ans:

Loss of token.