In this lesson students explore the benefits (and potential security concerns) associated with routing traffic across the Internet. Building on their introduction to IP addresses in the previous lesson, students use a version of the Internet Simulator that allows messages to be sent only to an intended recipient, as indicated by the IP address. The Internet Simulator also allows students to examine the traffic that goes through all of the (simulated) routers on the network. They will discover that messages go through many different routers, may not always take the same path to reach the final destination, and that the routers (and their owners) can *see all of this traffic*!
In this and the subsequent lesson, we consider some of the strategies used to construct networks and find paths for data in them. While this has a connection to ideas about the Internet, the focus of these lessons is on algorithms, formal techniques, and processes for solving problems. Students will explore and solve the Minimum Spanning Tree (MST) problem, first, in an unplugged fashion on paper. The real challenge is not in solving a particular instance of the minimum spanning tree, but to develop an algorithm, a clear series of steps, that if followed properly, will solve any instance of the problem. There is a possible misconception to look out for: the MST has a definite, verifiable optimal solution, as opposed to the Text Compression problem (from Unit 1), which does not.
In this lesson students will explore the Single Source Shortest Path problem, by solving the problem with pencil and paper first, then by following a famous algorithm that solves the shortest path problem known as Dijkstra’s Algorithm. Even though this is an algorithms detour, there is a strong connection in this lesson to routing algorithms used on the Internet. This lesson also introduces ideas about how we analyze algorithms: looking for correctness, efficiency and running time. As foreshadowing: in the next lesson students will act out another distributed shortest path algorithm used by routers to learn about the Internet dynamically.
This lesson is the last of the algorithm series. Building off of the previous lesson about shortest path algorithms, the activity in this lesson shows how routers learn about the rest of the Internet in order to route traffic so it takes the shortest path. In the previous lessons, students use the Internet Simulator to send packets to other students through simulated routers. The path that the packet follows, and how the router knows where to send it, however, has been largely untouched. Today, students simulate the process of a router joining a network and generating a router table that would allow them to send packets to anyone else in their network as efficiently as possible. They then reflect on the process by comparing the similarities between the SSSP problem and the process the used today, and how it facilitates the structure of the Internet.
In this lesson student develop a protocol for reliably sending a message over an unreliable internet. The Internet Simulator has been setup for this lesson to restrict messages to no more than 8 characters each, and messages get dropped messages with some probability on every hop.
Students are given time to experiment with the Internet Simulator and develop their own protocol, possibly testing or demonstrating their protocol to their peers. At the conclusion of the lesson, students watch a short video explaining how these challenges are addressed in the real world with [v TCP] - the Transmission Control Protocol.
The core idea of this lesson occurs in the unplugged activity that kicks off the lesson, in which students try to keep track of IP addresses that had been randomly assigned to each student in the class, while at the same time the teacher occasionally changes students' addresses. This leads to identifying the need for an authoritative system for name-to-address mappings, known as the Domain Name System or [v DNS].
Students then briefly experiment with a DNS protocol in the Internet Simulator. The activity is similar, in that students will have to grapple with IP addresses changing in real time and use the built in DNS protocol to resolve the issues.
The lesson ends with students doing some rapid research about DNS and some of its vulnerabilities, particularly what are known as Denial of Service Attacks.
In this lesson students are introduced to another high-level protocol of the Internet, [v HTTP]. The lesson begins with a review of the layers of the Internet covered thus far, before transitioning to a video covering high-level protocols of the Internet, most notably HTTP. Students will investigate HTTP traffic generated within their own browser by accessing the browser’s developer tools and visiting a variety of websites. A handout summarizing the structure of HTTP is provided to help students understand the components of the HTTP requests and responses they will observe. The lesson concludes with students sharing their findings with their classmates and a reflection on how the layers of the Internet make use of abstraction.
This lesson is a capstone to the Internet unit. Students will research and prepare a flash talk about an issue facing society: either **[v Net Neutrality]** or **Internet Censorship**. Developing an informed opinion about these issues hinges on an understanding of how the Internet functions as a system. Students will prepare and deliver a flash talk that should combine forming an opinion about the issue and an exhibition of their knowledge of the internet.
This lesson is good *practice* for certain elements of the AP Explore Performance Task.1 The primary things practiced here are: doing a bit of research about impacts of computing (though here it’s specifically about the Internet), explaining some technical details related to ideas in computer science, and connecting these ideas to global and social impacts. Students will practice synthesizing information, and presenting their learning in a flash talk.
1**Note:** This is NOT the official AP® Performance Task that will be submitted as part of the Advanced Placement exam; it is a practice activity intended to prepare students for some portions of their individual performance at a later time.
Welcome to Computer Science Principles! The first lesson is about getting students excited about the course and connecting their own personal interests to computer science. Students are asked to share something they know a lot about and teach it to a small group. Groups make a “rapid” prototype of an innovative idea and share it. Students watch a brief video about computing innovations. The lesson ends with students logging into the Code.org CSP course web site, and answering a brief prompt about what “computer science” means to them.
In this lesson students work in groups using classroom supplies and everyday objects to develop their own systems for encoding and sending simple binary messages, messages that only have two possible values. Students will think about what can be usefully conveyed in such a simple message and build a “device” to communicate the message over some physical distance.
Then students are asked to consider how to use their binary messaging devices to send a more complex message - a message with more than two possibilities, say four, or eight, or even thousands of different messages. Students will collaborate in an iterative design process in the “maker ethos” of rapidly building and improving their “device” for sending messages.
In this lesson, students will be introduced to how bits are transmitted over the most common mediums (copper wire, fiber-optic cable, and radio waves) used to connect devices on the Internet. They then chose a device that transmits bits and research that device and the system it uses. Students create a poster presenting their findings, and the lesson concludes with a gallery walk of the posters.
Students are introduced to the Internet Simulator, a tool they will return to many times in the first two units of the course. Today, the Internet Simulator will be used to simulate a single shared wire, connecting two people. The wire can only be in one of two possible states (state A or state B) and either partner may set or read the state of the wire at any time, but this is the only way in which students may communicate. Students must invent a binary call-response [v protocol] using this system. Coordination, speed and timing are problems that need to be solved. At the conclusion of the lesson, students compete to demonstrate the speed and accuracy of their protocols, and calculate the [v bit rate] of their message exchange.
Students will explore the properties of number systems by effectively inventing a base-3 number system using circles, triangles and squares as the symbols instead of arabic numerals. Students are asked to create rules that explain how each arrangement of symbols can be generated or predicated as an orderly, logical series. The objective is to understand that you can represent *any* number with any agreed-upon set of symbols that appear in an agreed-upon order. This is as true for circles, triangle and squares as it is for the digits 0-9, or the number systems we commonly see in computer science (binary and hexadecimal).
In this lesson, students will gain more familiarity with binary numbers. The lesson will transition away from the number systems that students created in the the circle-triangle-square activity, and begin to focus on representing numeric values using the binary number system. Though students have communicated with binary before, developing a *number system* is a little different. Previously, students mapped patterns of binary values to a small set of fixed messages. A number system is infinite, and also has rules for counting - or how to get from one value to the next.
In this lesson, students explore some fascinating stories from the news and history (and the future) about number encodings in computers. These stories should serve to illuminate how the kinds of decisions students have been making about number encodings are the same kinds of things that real scientists in the world have to worry about, sometimes with disastrous consequences. While this lesson has the possibility of running long, it is meant only as a short excursion into real-world application and should be limited to one class period.
In this lesson students will return to the Internet Simulator in order to send a simple line drawing to a classmate. Students will be presented a grid on which they will draw an image (connecting 3-7 dots with straight lines). They must develop a protocol which will allow them to send any image they might create on their grids, paying particular attention to how many bits are used to represent each binary number. Students will therefore have additional practice encoding and decoding binary numbers and develop further intuitions about the properties of binary numbers in a hands-on way. The lesson concludes by testing protocols using a teacher-supplied test-image to transmit.
In this lesson, students create their own system for representing text in binary and explore how their newfound ability to convert between binary and decimal numbers helps in this process. In the warm up students quickly create a system for representing the 50 states in binary. They then move to the main activity where they create a system for representing text using only numbers while communicating on the Internet Simulator. At the end of the main activity they briefly review the ASCII system. The wrap up discussion introduces the concept of abstraction and its connection to the chapter. Following this lesson there is a chapter assessment that reviews the contents of this and the previous lessons.
This lesson sets the the stage for why we want to learn about how the Internet works. First students share what they currently know about how the Internet works through a KWL activity.
Then students watch a short video the introduces Vint Cerf and the Internet at high level. Students then skim a memo written to the Internet Engineering Task Force (IETF) by Vint Cerf in 2002 entitled “The Internet is for Everyone,” which calls out a series of threats to the prospect that the Internet should be an open, easily and cheaply accessible resource for everyone on the planet.
Finally we foreshadow the practice PT at the end of the unit. Many of the questions and challenges raised by Vint Cerf still apply today, and students will be asked to research and present on one for the Practice PT.
In this lesson, students explore more deeply how communication between multiple computers can work over the Internet. They do this by playing a simplified game of Battleship, in which the first game is played unplugged, in their table groups, and the second game is played using the Internet Simulator, so that multiple students can connect to each other and see each other’s messages. Students must devise a messaging protocol that makes it clear who is sending the message and who the intended recipient is.
Students then devise a *binary protocol* for playing this game which will entail developing an addressing system for players, as a well as a formal packet structure for transmitting data about the state of the game.
**NOTE**: this is a large lesson that will likely need to span 2 days of class.
In this lesson students are introduced to the standard units for measuring the sizes of digital files, from a single byte, all the way up to terabytes and beyond. Students begin the lesson by comparing the size of a plain text file containing “hello” to a Word document with the same contents. Students are introduced to the units kilobyte, megabyte, gigabyte, and terabyte, and research the sizes of files they make use of every day, using the appropriate terminology. This lesson foreshadows an investigation of compression as a means for combatting the rapid growth of digital data.
At some point we reach a physical limit of how fast we can send bits and if we want to send a large amount of information faster, we have to find a way to represent the same information with fewer bits - we must **compress** the data.
In this lesson, students will use the Text Compression Widget to compress segments of English text by looking for patterns and substituting symbols for larger patterns of text. After some experimentation students are asked to come up with a process (or algorithm) for arriving at a "good" amount of compression despite the fact that there is no way to know what is best or optimal. In developing a so-called "[v heuristic] approach" to this problem, students will grapple with the tradeoffs in compressing data and begin to develop a sense of computing problems that are “hard” to solve.
In this lesson, students will begin to explore the way digital images are encoded in binary. The class begins by asking students to invent their own image encoding protocol in order to familiarize themselves with some of the subtle complications of encoding images, namely the need for other data, called [v metadata], that describes properties of the image necessary for rendering it. Students will learn about pixels, raster images, and what an image file format is. Students will encode binary image data using a widget in Code Studio.
In this lesson students are asked to consider how color is represented on a computer and to imagine how it might be encoded in binary. Students then learn about how color is actually represented on a computer - using the RGB color scheme - and create their own images in an new version of the pixelation widget that allows you use more than 1 bit per pixel to represent color information. After grappling with the prospect of possibly many bits just to represent a single pixel, students are shown how using hexadecimal allows us to represent many bits with fewer characters. Students use a new version of the pixelation tool to encode an image with color and create a personal favicon.
Students learn the difference between lossy and lossless compression by experimenting with a simple lossy compression widget for compressing text. Students then research three real-world compressed file formats to fill in a research guide. Throughout the process they review the skills and strategies used to research computer science topics online, in particular to cope with situations when they don't have the background to fully understand everything they're reading (a common situation even for experienced CS students).
In this lesson students will conduct a small amount of research to explore a file format either currently in use or from history. Students will conduct research in order to complete a "one-pager" that summarizes their findings. They will also design a computational artifact (video, audio, graphic, etc.) that succinctly summarizes the advantages of their format over other similar ones.
This lesson is intended to be a quick, short version of a performance task in which students rapidly do some research and respond in writing. It might take 2 class days but should not take more. The goal is to develop skills that students will use when they complete the actual Explore PT later in the year.
To conclude their introduction to programming, students will design a program that draws a digital scene of their choosing. Students will be working in groups of 3 or 4 and will begin by identifying a scene they wish to create. They will then use Top-Down Design to identify the high-level functions necessary to create that image. The group will then assign these components to individual members of the group to program. After programming their individual portion, students will combine all of their code to compose the whole scene. The project concludes with reflection questions similar to those students will see on the AP® Performance Tasks.
Note: This is NOT the official AP Performance Task that will be submitted as part of the Advanced Placement exam; it is a practice activity intended to prepare students for some portions of their individual performance at a later time.
AP® is a trademark registered and/or owned by the College Board, which was not involved in the production of, and does not endorse, this curriculum.
At the beginning of a new unit we jump right into an activity - building a small arrangement of LEGO® blocks and then creating text instructions a classmate could follow to construct the same arrangement. Groups will then trade instructions to see if they were clear enough to allow reconstruction of the original arrangement. The wrap-up discussion is used to highlight the inherent ambiguities of human language and call out the need for the creation of a programming language which leaves no room for interpretation.
This is the 2nd day of a 3-lesson sequence in which we attempt to show the "art" of programming and introduce the connection between programming and algorithms. In the previous lesson we established the need for a common language with which express algorithms to avoid ambiguity in how instructions would be interpreted. In this lesson we continue to establish the connection between programming and algorithms, with more emphasis on the "art" of algorithms.
First students are presented with a new task for the “human machine” - to write a set of instructions to identify the smallest (lowest value) card in row of cards on the table. Once again we try to establish a set of fundamental commands for doing this, and develop a more formal set of “low-level” commands for manipulating playing cards. Students are presented with a "Human Machine Language" that includes 5-commands and then must figure out how to use these primitive commands to “program” the same algorithm.
At the conclusion several points about programming can be made, namely: 1. Different algorithms can be developed to solve the same problem 2. Different programs can be written to implement the same algorithm.
This is the third of three lessons that make the connection between programming and algorithms. In this lesson students continue to work with the "Human Machine Language" to get creative designing more algorithms for playing cards. One command is added to the language from the previous lesson (SWAP) that allows positions of cards to change. With the addition of swap the challenge is to design an algorithm that will move the minimum card to the front of the list while keeping the relative order of all the other cards the same. If that is achieved some other Human Machine Language challenges are available.
This lesson is a student's first exposure to programming in App Lab. The lesson begins with a quick reflection prompt. Then students are introduced to the practice of pair programming before beginning to program. For this lesson the students' view is limited to only a very few simple “turtle” commands to draw graphics on the screen. After a few warm up exercises, using only combinations of four drawing commands, students must figure out the most “efficient” way to draw an image of a 3x3 grid. The lesson concludes with a sense-making discussion about the meaning of efficiency in programming and the reason behind beginning with such a limited set of programming tools.
At the end of the lesson students review the concept of abstraction and are introduced to elements of the Create PT in preparation for the Practice PT at the end of the unit.
This lesson presents a top-down problem-solving strategy for designing solutions to programming problems. Students use a worksheet to learn about top-down design, and then on paper, design a solution to a new turtle drawing challenge with a partner. Having practiced this approach on paper and in code, students will be re-presented with the 3x3 square challenge from an earlier lesson and asked to improve upon their old solution by designing multiple layers of functions.
Students will learn to read App Lab’s API documentation and will use functions that accept parameters in order to complete a series of drawing puzzles which require them to make use of the App Lab API documentation to learn new drawing commands. Many of these commands will require the use of parameters. The final challenge asks students to design a personal monogram making use of the commands they learned during the lesson.
In this lesson, students practice using and creating functions with parameters. Students learn that writing functions with parameters can generalize solutions to problems even further. Especially in situations where feel like you are about to duplicate some code with only a few changes to some numbers, that is a good time to write a function that accepts parameters. In the second half of the lesson, students make a series of modifications to a program that creates an “Under the Sea” scene by adding parameters to functions to more easily add variation to the scene. Lastly, students are introduced to App Lab’s random number functions to supply random values to function calls so the scene looks a little different every time the program runs.
Students learn to use random values and looping to create variation in their drawings and quickly duplicate objects they wish to appear in their digital scenes many times. Students will be presented with a version of the for loop which only enables them to change the number of times the loop runs. This block is essentially a "repeat" block and will be presented that way. Students will also be presented with blocks which enable them to choose a random number within a given range. Together these blocks enable students to create more complex backgrounds for digital scenes by randomly placing simple objects within the background of their scene. Students use these tools to step through the Under the Sea exemplar digital scene.
To conclude their study of big data and cryptography, students will complete a small research project related to a dilemma presented by Big Data or Cybersecurity, in the form of a Practice Performance Task. Students will pick one of two issues to research more deeply - either an issue related to big data, or one related to cybersecurity. Students will need to identify appropriate online resources to learn about the functionality, context, and impact of the technological innovation that gave rise to the dilemma they are investigating. After completing their research, students will present their findings both in a written summary and with an audio / visual artifact they found online. The written components students must complete are similar to those students will see in the AP Performance Tasks.
This project is an opportunity to practice many of the skills students will use when completing the Explore Performance Task on the AP® Exam at the end of the year. While an open-ended research project might be intimidating, students have built all the skills they need to complete this task.
**Note:** This is NOT the official AP® Performance Task that will be submitted as part of the Advanced Placement exam; it is a practice activity intended to prepare students for some portions of their individual performance at a later time.
**Note for 2017-18 School Year:** This Practice PT has NOT been updated to reflect changes to the [Explore PT Scoring Guidelines](https://apcentral.collegeboard.org/pdf/2018-explore-performance-tasks-sg.pdf) released in Fall 2017. We recommend you review those guidelines to understand the similarities between this project and the actual Explore PT.
Students learn about various types of cybercrimes and the cybersecurity measures that can help prevent them. Then students perform a Rapid Research project investigating a particular cybercrime event with a particular focus on the data that was lost or stolen and the concerns that arise as a result. The Rapid Research activity features vocabulary, concepts, and skills that should help prepare them for the AP Explore PT, and also serves as a capstone for the sequence of lessons on encryption and security.
In this lesson, students are introduced to the concept of “[v big data],” where it comes from, what makes it “big,” and how people use big data to solve problems. Students are asked to consider how much of their lives are “datafied” or could be, and the teacher will show the projected growth of data in the world. Students will then investigate a big data tool in pairs to evaluate the tool for its usefulness and investigate the source of the data used to make the tool. A key take-away from the lesson is that different considerations need to be made when trying to look at, use, or analyze tools that use big data. The world of big data is big, and we’ve only begun to figure out how to solve problems with it.
The lesson concludes with a brief introduction to the AP Explore Performance Task which students are recommended to complete at the end of the unit.
Students use the Google Trends tool in order to visualize historical search data. They will need to identify interesting trends or patterns in their findings and will attempt to explain those trends, based on their own experience or through further research online. Afterwards, students will present their findings to ensure they are correctly identifying patterns in a visualization and are providing plausible explanations of those patterns.
This lesson asks students to consider carefully the assumptions they make when interpreting data and data visualizations. The class begins by examining how the Google Flu Trends project tried and failed to use search trends to predict flu outbreaks. They will then read a report on the Digital Divide which highlights how access to technology differs widely by personal characteristics like race and income. This report challenges a widespread assumption that data collected online is representative of the population at large. To practice identifying assumptions in data analysis, students are provided a series of scenarios in which data-driven decisions are made based on flawed assumptions. They will need to identify the assumptions being made (most notably those related to the digital divide) and explain why these assumptions lead to incorrect conclusions.