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AP Computer Science Principles Unit 4: Computer Systems and Networks

12 questions

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Unit 4: Computer Systems and Networks

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Question 1

Which of the following BEST describes the role of a router on the Internet?

A.A router stores web pages so users can access them faster.B.A router encrypts data before it leaves a device's network interface.C.A router forwards packets from one network to another, choosing the path each packet should take toward its destination.D.A router assigns unique usernames and passwords to each device on the network.

Question 2

A program runs four tasks. Tasks A and B can run in parallel (no dependencies between them). Task C depends on the output of Task A. Task D depends on the outputs of both B and C.

Task A: 3 seconds
Task B: 5 seconds
Task C: 2 seconds (starts after A)
Task D: 1 second (starts after B and C both finish)

Assuming unlimited parallel processors, what is the minimum time to complete all four tasks?

A.6 secondsB.8 secondsC.11 secondsD.5 seconds

Question 3

A company hosts its website on a single server in one data center. The website goes down whenever the data center loses power. Which of the following upgrades would MOST improve the website's fault tolerance?

A.Upgrading the server's processor to a faster model.B.Compressing the website's files so they take less storage space.C.Encrypting all connections using HTTPS.D.Replicating the website on servers in multiple geographically distributed data centers, with traffic rerouted automatically when one center goes down.

Question 4

A pipeline to process data consists of three sequential stages that cannot be parallelized: Stage 1 takes 2 seconds, Stage 2 takes 8 seconds, Stage 3 takes 3 seconds. A programmer proposes splitting Stage 2 into four equal parallel tasks (each 2 seconds) running on four processors simultaneously.

What is the total pipeline time after this optimization?

A.4 secondsB.7 secondsC.13 secondsD.3.25 seconds

Question 5

Which of the following BEST describes what TCP (Transmission Control Protocol) adds to the basic packet-delivery service of IP?

A.TCP encrypts each packet so that only the intended recipient can read it.B.TCP guarantees reliable, ordered delivery — it detects lost packets and requests retransmission, and reassembles data in the correct order.C.TCP assigns an IP address to each device on the network.D.TCP determines which physical path packets take through the network.

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Question 6

The Internet was designed so that if one path between two computers is unavailable, data can still reach its destination by taking a different path. This property is called:

A.EncryptionB.AbstractionC.Fault toleranceD.Scalability

Question 7

A university uses a single server to host its website. As enrollment grows, the website becomes slow for users. The IT department adds two more identical servers and distributes incoming web requests evenly among all three.

This approach BEST demonstrates which computing concept?

A.Sequential computing — the three servers process one request at a time in order.B.Distributed computing — workload is spread across multiple servers to improve performance and scalability.C.Fault tolerance — the extra servers ensure the site never goes down.D.Encryption — data is split across three servers so no single server has the complete message.

Question 8

A wireless network uses radio waves to transmit data from a laptop to a router. The router connects to the Internet via a fiber optic cable. At each step in this transmission, what is the fundamental representation of data?

A.Text characters in the wireless segment and binary digits in the fiber segment.B.Binary sequences (bits) at all stages — represented as radio wave patterns in the wireless segment and as light pulses in the fiber segment.C.Analog signals throughout, since radio waves and light are inherently analog.D.Decimal numbers in the wireless segment converted to binary only when entering the fiber cable.

Question 9

The Internet protocol stack is organized into layers, where each layer provides services to the layer above it and uses services from the layer below it. Which of the following BEST describes why this layered (abstraction) model is useful?

A.The layered model forces all Internet traffic to travel through a central server that manages routing for the entire Internet.B.The layered model allows each layer to be changed or upgraded independently without affecting other layers, as long as the interface between layers stays the same.C.The layered model encrypts each layer's data before passing it down, providing security at every level.D.The layered model eliminates packet loss by duplicating packets at each layer.

Question 10

Two tasks must be completed: Task A takes 6 minutes and Task B takes 4 minutes. If run sequentially, total time is 10 minutes. If run in parallel on two processors, what is the minimum possible time to complete BOTH tasks?

A.2 minutesB.5 minutesC.6 minutesD.10 minutes

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Question 11

Which of the following BEST describes the concept of open protocols on the Internet?

A.Open protocols mean the Internet has no security and anyone can read all data transmitted.B.Open protocols are publicly documented standards that allow any device or software from any manufacturer to communicate on the Internet.C.Open protocols are owned by a single company that licenses them to other manufacturers.D.Open protocols require all devices to use the same operating system to ensure compatibility.

Question 12

On the Internet, data is sent as small units called packets. Which of the following BEST describes why packets are used instead of sending the entire message as one continuous stream?

A.Packets allow data to travel at faster-than-light speeds through fiber optic cables.B.Packets allow multiple messages to share network paths, enable rerouting around failures, and permit out-of-order delivery that can be reassembled at the destination.C.Packets encrypt the data so it cannot be read while in transit.D.Packets are used only for audio and video streaming; text is still sent as a continuous stream.

AP Computer Science Principles Unit 4: Computer Systems and Networks — Free with Answer Explanations | Test Practice Hub