Unit 4: Computer Systems & Networks
CS Principles · Unit 4 · Paper 1

Computer Systems & Networks unit test

A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.

Paper 1Paper 2Paper 3
Each paper is built from this unit’s 28 terms and is the same for everyone, so a teacher can assign “Unit 4, Paper 1” and every student sits the identical test. Multiple choice is marked objectively; the written sections you mark yourself against the model answer and rubric.
Suggested time 33 min 30 points0/17 attempted
1

DNS

2

Bit rate

3

Packet switching

4

Scalability of the Internet

5

Computer network

6

TCP

7

Protocol

8

World Wide Web vs the Internet

9

Computing system

10

Redundancy

11

HTTP

12

UDP

Short answer 1. Define or explain: Fault tolerance

3 pts

Short answer 2. Define or explain: Why a network diagram question is about paths

3 pts

Short answer 3. Define or explain: Open protocol

3 pts

Short answer 4. Define or explain: Parallel computing on a network

3 pts

Free response

6 pts

This course has no free-response prompt tagged to this unit, so one from elsewhere in the course is used. It is still worth writing — the skill transfers.

A programmer writes the following procedure, intending it to return the number of values in a list that are greater than a given threshold. List indexes begin at 1. PROCEDURE countAbove(values, limit) { count ← 0 i ← 1 REPEAT UNTIL (i > LENGTH(values)) { IF (values[i] > limit) { count ← count + 1 } } RETURN(count) }

Trace the call countAbove([5, 12, 3], 4) and describe exactly what happens.

Identify the error and state the single change that fixes it.

After the fix, state what countAbove([5, 12, 3], 4) returns and what countAbove([1, 2], 9) returns.

Explain how you would test the corrected procedure to be confident it is right, and describe how the number of steps grows as the list gets longer.