📚 Experiment/Practical Assessment Key Points | 实验/实践考核要点
Practical assessment in CIE IGCSE Computer Science tests your ability to design solutions, write algorithms in pseudocode or flowcharts, and understand program logic — not just your typing speed. This guide walks you through the key concepts, common pitfalls, and marking essentials to help you score highly on Paper 2.
CIE IGCSE 计算机科学的实践考核重在考查你设计解决方案、用伪代码或流程图编写算法以及理解程序逻辑的能力，而不仅仅是打字速度。本文将带你梳理关键概念、常见失分点和评分要点，帮助你在 Paper 2 中取得高分。
1. Understanding the Practical Assessment Format | 了解实践考核形式
Paper 2 of the CIE IGCSE Computer Science (0478) is a written paper, not an on-screen coding test. You will be presented with problem scenarios and asked to design algorithms using pseudocode, draw flowcharts, write program code in a high-level language (often Python, Visual Basic or Pascal), and answer logic gate questions. All answers are handwritten, so clear structure matters.
CIE IGCSE 计算机科学（0478）的 Paper 2 是笔试，而不是上机编程考试。你将面对问题场景，要求使用伪代码设计算法、绘制流程图、用高级语言（通常是 Python、Visual Basic 或 Pascal）编写程序代码，并回答逻辑门相关题目。所有答案均需手写，因此清晰的卷面结构至关重要。
2. Writing Effective Algorithms | 编写高效算法
An algorithm must be precise, complete and logically ordered. Begin by identifying inputs, processes and outputs. Break the solution into small steps, and always consider edge cases. Examiners reward clarity, so do not rush into code — plan first with a brief note or a rough sketch.
算法必须精确、完整且逻辑有序。先确定输入、处理和输出，将解决方案分解为小步骤，并始终考虑边界情况。考官看重的是清晰的思路，因此不要急着写代码，先用简要注释或草图做好规划。
3. Flowchart Design Tips | 流程图设计技巧
Use the standard symbols correctly: oval for Start/End, parallelogram for Input/Output, rectangle for Process, diamond for Decision, and arrows for flow direction. Labels must be brief but descriptive. All paths should eventually reach an End symbol, and decision diamonds must have exactly two outgoing arrows labelled Yes/No or True/False.
正确使用标准符号：椭圆形表示开始/结束，平行四边形表示输入/输出，矩形表示处理过程，菱形表示判断，箭头表示流程方向。标注文字应简洁明了。所有路径最终都要到达结束符号，判断菱形必须有且仅有两个出口，并标注是/否或真/假。
4. Pseudocode Essentials | 伪代码基础要点
CIE does not specify a strict pseudocode syntax, but you must be consistent. Use indentation to show structure, write keywords in capitals (e.g. IF … THEN … ELSE … ENDIF, FOR … TO … NEXT, WHILE … DO … ENDWHILE), and avoid language-specific features like Python's list comprehensions unless permitted. Keep statements simple and readable.
CIE 没有规定严格的伪代码语法，但你必须保持风格一致。用缩进体现结构，关键词大写（如 IF … THEN … ELSE … ENDIF, FOR … TO … NEXT, WHILE … DO … ENDWHILE），避免使用语言特有的功能（如 Python 的列表推导式），除非题目允许。语句要简洁易读。
5. Data Types and Variables | 数据类型与变量
Clearly declare variables with sensible names and appropriate data types: INTEGER, REAL, CHAR, STRING, BOOLEAN. Use meaningful identifiers like totalMark instead of x. In pseudocode, you can simply state DECLARE totalMark AS INTEGER. Remember that a variable must be initialised before it is used in a calculation.
要用有意义的名称声明变量并指定合适的数据类型：INTEGER, REAL, CHAR, STRING, BOOLEAN。用诸如 totalMark 而非 x 这样的有意义的标识符。在伪代码中，可以写成 DECLARE totalMark AS INTEGER。记住变量在参与运算之前必须先初始化。
6. Control Structures: Sequence, Selection, Iteration | 控制结构：顺序、选择、循环
Every problem can be solved using only sequence, selection and iteration. Sequence means executing statements one after another. Selection uses IF or CASE statements to make decisions. Iteration uses FOR loops (when you know the number of repetitions) or WHILE/REPEAT loops (when you depend on a condition). Always ensure loops have a clear exit condition to avoid infinite loops.
任何问题都可以仅用顺序、选择和循环来解决。顺序指逐条执行语句。选择用 IF 或 CASE 语句做判断。循环用 FOR 循环（已知重复次数）或 WHILE/REPEAT 循环（取决于条件）。务必确保循环有明确的退出条件，避免死循环。
7. Working with Arrays | 数组的使用
Arrays store multiple values of the same data type under a single name. You must know how to declare a 1D array (e.g. DECLARE marks[30] AS INTEGER), access elements using an index, and iterate through an array with a loop. For 2D arrays, use row and column indices. Common tasks include finding the maximum, calculating totals, and searching for a value.
数组用一个名字存储多个相同数据类型的值。你必须掌握如何声明一维数组（如 DECLARE marks[30] AS INTEGER）、使用索引访问元素，以及用循环遍历数组。对于二维数组，要使用行索引和列索引。常见任务包括找最大值、计算总和以及查找某个值。
| Task / 任务 | Pseudocode Example / 伪代码示例 |
|---|---|
| Find maximum / 找最大值 | max ← arr[0] |
8. Input/Output and Validation | 输入输出与数据验证
Use INPUT and OUTPUT (or PRINT) commands to interact with the user. Always validate input data when required: check for range, type, length or format. A typical validation routine uses a WHILE loop that repeats until a valid input is entered. Never assume the user will enter correct data.
使用 INPUT 和 OUTPUT（或 PRINT）命令与用户交互。只要题目有要求，一定要对输入数据进行验证：检查范围、类型、长度或格式。典型的验证例程使用 WHILE 循环，直到输入有效数据为止。绝不能假设用户会输入正确的数据。
9. Testing and Debugging | 测试与调试
Testing is an explicit part of the markscheme. Provide a test table with normal data, boundary data (just inside, on, and just outside limits) and erroneous data. Walk through your algorithm mentally to catch logic errors. In pseudocode questions, you may be asked to identify and correct errors in a given piece of code.
测试是评分标准中明确的一部分。提供测试用表，包含正常数据、边界数据（刚好在边界内、边界上和边界外）以及错误数据。在心里过一遍算法，找出逻辑错误。在伪代码题目中，可能会让你找出并改正一段给定代码中的错误。
10. Logic Gates and Truth Tables | 逻辑门与真值表
You must know the symbols and truth tables for NOT, AND, OR, NAND and NOR gates. Be prepared to draw a logic circuit from a Boolean expression or a truth table, and to complete a truth table for a given combination of gates. Use standard symbols: a triangle with a small circle for NOT, a D-shaped curve for AND, and a curved shape with a point for OR.
你必须掌握 NOT、AND、OR、NAND 和 NOR 门的符号和真值表。要准备好根据布尔表达式或真值表绘制逻辑电路，并为给定的门组合填写真值表。使用标准符号：NOT 门用三角形加小圆圈，AND 门用 D 形曲线，OR 门用带尖的弧形。
Example: NOT (A AND B) gives NAND gate logic.
示例：NOT（A AND B）得到 NAND 门逻辑。
11. Common Mistakes to Avoid | 要避免的常见错误
Many students lose marks by forgetting to initialise variables, using assignment and comparison operators incorrectly (e.g. = for both in pseudocode is acceptable, but in code languages = vs == causes errors), mixing up PRINT and OUTPUT syntax, or drawing incomplete flowcharts. Also, never leave an IF statement without a matching ENDIF, or a loop without a terminating condition.
许多学生因为忘记初始化变量、混淆赋值与比较运算符（例如，伪代码中 = 可以用于两者，但在代码语言中 = 和 == 混用会出错）、搞混 PRINT 和 OUTPUT 语法，或绘制不完整的流程图而丢分。另外，切勿遗漏与 IF 配对的 ENDIF，或让循环缺少终止条件。
12. Final Preparation Tips | 最终准备建议
Practise past Paper 2 questions under timed conditions. After writing a solution, always check against the markscheme to see what the examiner expects. Memorise the standard algorithms for linear search, maximum/minimum, counting and running totals. On the day, read each question twice, and ensure your diagrams are neatly drawn with a ruler and pencil.
在限时条件下练习往年 Paper 2 的题目。写完答案后，一定要对照评分标准看看考官的期望是什么。熟记线性搜索、最大值/最小值、计数和累加求和的标准算法。考试当天，每道题读两遍，并确保用尺子和铅笔整洁地绘制图表。
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