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Standard:
Compare levels of abstraction and interactions between application software, system software, and hardware.

Descriptive Statement:
At its most basic level, a computer is composed of physical hardware on which software runs. Multiple layers of software are built upon various layers of hardware. Layers manage interactions and complexity in the computing system. System software manages a computing device's resources so that software can interact with hardware. Application software communicates with the user and the system software to accomplish its purpose. Students compare and describe how application software, system software, and hardware interact. For example, students could compare how various levels of hardware and software interact when a picture is to be taken on a smartphone. Systems software provides low-level commands to operate the camera hardware, but the application software interacts with system software at a higher level by requesting a common image file format (e.g., .png) that the system software provides.

Standard:
Describe issues that impact network functionality.

Descriptive Statement:
Many different organizations, including educational, governmental, private businesses, and private households rely on networks to function adequately in order to engage in online commerce and activity. Quality of Service (QoS) refers to the capability of a network to provide better service to selected network traffic over various technologies from the perspective of the consumer. Students define and discuss performance measures that impact network functionality, such as latency, bandwidth, throughput, jitter, and error rate. For example, students could use online network simulators to explore how performance measures impact network functionality and describe impacts when various changes in the network occur. Alternatively, students could describe how pauses in television interviews conducted over satellite telephones are impacted by networking factors such as latency and jitter.

Standard:
Describe the design characteristics of the Internet.

Descriptive Statement:
The Internet connects devices and networks all over the world. Large-scale coordination occurs among many different machines across multiple paths every time a web page is opened or an image is viewed online. Through the domain name system (DNS), devices on the Internet can look up Internet Protocol (IP) addresses, allowing end-to-end communication between devices. The design decisions that direct the coordination among systems composing the Internet also allow for scalability and reliability. Students factor historical, cultural, and economic decisions in their explanations of the Internet. For example, students could explain how hierarchy in the DNS supports scalability and reliability. Alternatively, students could describe how the redundancy of routing between two nodes on the Internet increases reliability and scales as the Internet grows.

Standard:
Compare and contrast security measures to address various security threats.

Descriptive Statement:
Network security depends on a combination of hardware, software, and practices that control access to data and systems. The needs of users and the sensitivity of data determine the level of security implemented. Potential security problems, such as denial-of-service attacks, ransomware, viruses, worms, spyware, and phishing, present threats to sensitive data. Students compare and contrast different types of security measures based on factors such as efficiency, feasibility, ethical impacts, usability, and security. At this level, students are not expected to develop or implement the security measures that they discuss. For example, students could review case studies or current events in which governments or organizations experienced data leaks or data loss as a result of these types of attacks. Students could provide an analysis of actual security measures taken comparing to other security measure which may have led to different outcomes. Alternatively, students might discuss computer security policies in place at the local level that present a tradeoff between usability and security, such as a web filter that prevents access to many educational sites but keeps the campus network safe.

Standard:
Compare and contrast cryptographic techniques to model the secure transmission of information.

Descriptive Statement:
Cryptography is a technique for transforming information on a computer in such a way that it becomes unreadable by anyone except authorized parties. Cryptography is useful for supporting secure communication of data across networks. Examples of cryptographic methods include hashing, symmetric encryption/decryption (private key), and assymmetric encryption/decryption (public key/private key). Students use software to encode and decode messages using cryptographic methods. Students compare the costs and benefits of using various cryptographic methods. At this level, students are not expected to perform the mathematical calculations associated with encryption and decryption. For example, students could compare and contrast multiple examples of symmetric cryptographic techiques. Alternatively, students could compare and contrast symmetric and asymmetric cryptographic techniques in which they apply for a given scenario.

Standard:
Compare and contrast fundamental data structures and their uses.

Descriptive Statement:
Data structures are designed to provide different ways of storing and manipulating data sets to optimize various aspects of storage or runtime performance. Choice of data structures is made based on expected data characteristics and expected program functions. Students = compare and contrast how basic functions (e.g.., insertion, deletion, and modification) would differ for common data structures including lists, arrays, stacks, and queues. For example, students could draw a diagram of how different data structures change when items are added, deleted, or modified. They could explain tradeoffs in storage and efficiency issues. Alternatively, when presented with a description of a program and the functions it would be most likely to be running, students could list pros and cons for a specific data structure use in that scenario.

Standard:
Demonstrate the flow of execution of a recursive algorithm.

Descriptive Statement:
Recursion is a powerful problem-solving approach where the problem solution is built on solutions of smaller instances of the same problem. A base case, which returns a result without referencing itself, must be defined, otherwise infinite recursion will occur. Students represent a sequence of calls to a recursive algorithm and show how the process resolves to a solution. For example, students could draw a diagram to illustrate flow of execution by keeping track of parameter and returned values for each recursive call. Alternatively, students could create a video showing the passing of arguments as the recursive algorithm runs.

Standard:
Plan and develop programs for broad audiences using a specific software life cycle process.

Descriptive Statement:
Software development processes are used to help manage the design, development, and product/project management of a software solution. Various types of processes have been developed over time to meet changing needs in the software landscape. The systems development life cycle (SDLC), also referred to as the application development life cycle, is a term used in systems engineering, information systems, and software engineering to describe a process for planning, creating, testing, and deploying an information system. Other examples of common processes could include agile, spiral, or waterfall. Students develop a program following a specific software life cycle process, with proper scaffolding from the teacher. For example, students could work in teams on a common project using the agile development process, which is based on breaking product development work into small increments. Alternatively, students could be guided in implementing sprints to focus work on daily standup meetings or scrums to support efficient communication.

Standard:
Develop programs for multiple computing platforms.

Descriptive Statement:
Humans use computers in various forms in their lives and work. Depending on the situation, software solutions are more appropriate or valuable when available on different computational platforms or devices. Students develop programs for more than one computing platform (e.g. desktop, web, or mobile). For example, students could develop a mobile app for a location-aware software product and a different program that is installed on a computer. Alternatively, students could create a browser-based product and make it accessible across multiple platforms or computers (e.g., email).

Standard:
Identify and fix security issues that might compromise computer programs.

Descriptive Statement:
Some common forms of security issues arise from specific programming languages, platforms, or program implementation choices. Students read a given a piece of code that contains a common security vulnerability, explain the code's intended function or purpose, provide and explain examples of how a specific input could exploit that vulnerability (e.g., the program accessing data or performing in unintended ways), and implement a change in the code to mitigate this vulnerability. For example, students could review code that takes a date as input, recognize that the code doesn't check for appropriate last days of the month, and modify the code to do that. Alternatively, students could review code that supports entry of patient data (e.g., height and weight) and doesn't prompt users to double check unreasonable values (e.g., height at 6 feet and weight at 20 pounds).