📚 Case Study Practice: A Hands-on Approach to KS3 CAIE Computer Science | 案例分析实战演练：KS3 CAIE 计算机
In KS3 CAIE Computer Science, mastering computational thinking and programming requires more than just theory — you need to apply your knowledge to real-world scenarios. This article presents a hands-on case study where we design, develop, and evaluate a simple ‘Guess the Number’ game. You will see how to break down a problem, create algorithms, draw flowcharts, write pseudocode, implement code, test it, and reflect on improvements. Each stage reinforces key skills such as decomposition, pattern recognition, abstraction, and algorithm design — exactly what you need for your assessments and beyond.
在 KS3 CAIE 计算机课程中，掌握计算思维和编程不仅需要理论知识——你还需要将知识应用到实际场景中。本文呈现一个动手实践的案例分析，我们设计、开发并评估一个简单的“猜数字”游戏。你将看到如何分解问题、创建算法、绘制流程图、编写伪代码、实现代码、测试并反思改进。每个阶段都强化了分解、模式识别、抽象和算法设计等关键技能——这正是你应对评估以及未来学习所需的。
1. Understanding the Problem | 理解问题
The first step in any project is to define exactly what we want to achieve. For our Guess the Number game, the computer selects a random integer between 1 and 100, and the player tries to guess it. After each guess, the computer responds with ‘Too high’, ‘Too low’, or ‘Correct!’. The game continues until the guess is correct.
任何项目的第一步都是明确定义我们要实现什么。对于我们的猜数字游戏，计算机随机选择一个1到100之间的整数，玩家试图猜出这个数。每次猜测后，计算机给出“太高”、“太低”或“正确！”的回应。游戏持续进行直到猜对。
We also need to consider user experience: the game should be easy to understand and play, with clear prompts. It should handle invalid inputs gracefully, such as entering letters, decimals, or numbers outside 1–100. Additionally, we may want to track the number of attempts and display a final score.
我们还需要考虑用户体验：游戏应该易于理解和操作，并有清晰的提示。它应该妥善处理无效输入，例如输入字母、小数或超出1–100范围的数字。此外，我们可能希望跟踪猜测次数并显示最终得分。
2. Decomposition | 分解问题
Decomposition means breaking a complex problem into smaller, manageable parts. For the Guess the Number game, we can identify these subtasks: (1) Generate a random number; (2) Show a welcome message and prompt for a guess; (3) Read the player’s input and validate it; (4) Compare the guess with the secret number; (5) Display the appropriate feedback (too high, too low, or correct); (6) Repeat until the guess is correct or a limit is reached; (7) Display a closing message, including the number of attempts.
分解意味着将一个复杂问题拆分成更小、更易管理的部分。对于猜数字游戏，我们可以识别出以下子任务：(1) 生成一个随机数；(2) 显示欢迎信息并提示猜测；(3) 读取玩家输入并验证其有效性；(4) 将猜测与秘密数字进行比较；(5) 显示适当的反馈（太高、太低或正确）；(6) 重复直到猜对或达到限制；(7) 显示结束信息，包括猜测次数。
By breaking down the problem, each part can be tackled individually and then integrated into a complete solution. This approach makes development more organized and simplifies debugging and testing.
通过分解问题，每个部分都可以单独处理，然后整合成一个完整的解决方案。这种方法使开发更有条理，并简化了调试与测试。
3. Algorithm Design | 算法设计
Let’s write the step-by-step algorithm in plain English. This sequence of actions will be the blueprint for our program.
让我们用简单的英语编写分步算法。这个动作序列将是我们程序的蓝图。
Step 1: Set a variable secret_number to a random integer between 1 and 100.
步骤1：将变量 secret_number 设置为1到100之间的一个随机整数。
Step 2: Set attempts to 0.
步骤2：将 attempts 设为0。
Step 3: Display a message asking the player to guess a number between 1 and 100.
步骤3：显示一条信息，要求玩家猜一个1到100之间的数字。
Step 4: Read the player’s input and store it in guess.
步骤4：读取玩家的输入并将其存储在 guess 中。
Step 5: If the input is not a valid integer, display an error message and go back to Step 3.
步骤5：如果输入不是有效的整数，显示错误信息并返回到步骤3。
Step 6: Increment attempts by 1.
步骤6：将 attempts 增加1。
Step 7: If guess equals secret_number, display ‘Correct! You guessed it in X attempts.’ and end the program.
步骤7：如果 guess 等于 secret_number，显示“正确！你在 X 次猜测中猜对了。”并结束程序。
Step 8: If guess is greater than secret_number, display ‘Too high.’
步骤8：如果 guess 大于 secret_number，显示“太高”。
Step 9: If guess is less than secret_number, display ‘Too low.’
步骤9：如果 guess 小于 secret_number，显示“太低”。
Step 10: Go back to Step 3 (loop until the guess is correct).
步骤10：返回步骤3（循环直到猜对）。
4. Flowchart Representation | 流程图表示
A flowchart uses standard symbols to visualise the algorithm. We begin with an oval ‘Start’ symbol. A rectangle represents generating the secret number and initialising attempts. A parallelogram is used for outputting the prompt and inputting the guess. Next, a diamond decision symbol checks if the guess equals the secret number. If true, the flow goes to a parallelogram outputting the success message, and then to an oval ‘End’. If false, another diamond checks whether the guess is too high or too low, outputs the hint, and loops back to the input symbol. Arrows show the direction of flow.
流程图使用标准符号将算法可视化。我们从一个椭圆形的“开始”符号开始。矩形表示生成秘密数字并初始化 attempts。平行四边形用于输出提示和输入猜测。接下来，一个菱形判断符号检查猜测是否等于秘密数字。如果为真，流程走到输出成功消息的平行四边形，然后到椭圆形“结束”。如果为假，另一个菱形检查猜测是太高还是太低，输出提示，并循环回到输入符号。箭头表示流程方向。
The symbols used are: Oval for Start/End, Rectangle for process, Parallelogram for input/output, and Diamond for decision. This visual tool helps programmers see the logic and spot any missing steps before writing code.
使用的符号是：椭圆表示开始/结束，矩形表示处理过程，平行四边形表示输入/输出，菱形表示判断。这个可视化工具可以帮助程序员在编写代码前看清逻辑并发现任何遗漏的步骤。
5. Pseudocode | 伪代码
Pseudocode is a text-based description of the algorithm using structured English that resembles programming languages but without strict syntax. Below is the pseudocode for our game. The right column provides the Chinese translation for each step.
伪代码是用结构化英语对算法的文本描述，它类似于编程语言但没有严格的语法。下面是我们的游戏的伪代码。右侧列提供每个步骤的中文翻译。
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