Algorithms, Programming and Logic | 算法、编程与逻辑

📚 Algorithms, Programming and Logic | 算法、编程与逻辑

In Cambridge IGCSE Computer Science, algorithms, programming and logic form the core of computational thinking. An algorithm is a precise sequence of steps for solving a problem; programming turns an algorithm into code; logic underpins conditions, decisions and electronic circuits. This article covers the key ideas you need for the exam: algorithm design, pseudocode, flowcharts, sequence, selection, iteration, operators, truth tables, logic gates, trace tables, testing, subprograms and debugging.

在剑桥 IGCSE 计算机科学中，算法、编程和逻辑是计算思维的核心。算法是解决问题的精确步骤序列；编程将算法转化为代码；逻辑是条件、决策和电子电路的基础。本文涵盖考试所需的关键概念：算法设计、伪代码、流程图、顺序、选择、迭代、运算符、真值表、逻辑门、追踪表、测试、子程序和调试。

1. What Is an Algorithm? | 什么是算法？

An algorithm is a step-by-step set of instructions for solving a problem or completing a task. In the IGCSE Computer Science exam, an algorithm must be finite, precise, unambiguous and able to produce correct outputs for given inputs. Everyday examples include recipes, directions to a destination and instructions for making a cup of tea.

算法是解决问题或完成任务的一组逐步指令。在 IGCSE 计算机科学考试中，算法必须有限、精确、无歧义，并能对给定输入产生正确输出。日常例子包括食谱、前往目的地的路线以及泡茶说明。

When designing algorithms, you should break a problem into smaller sub-problems, identify the inputs and outputs, then decide the main steps. This process is called decomposition and is part of computational thinking.

设计算法时，应将问题分解为更小的子问题，确定输入和输出，然后确定主要步骤。这个过程称为分解，是计算思维的一部分。

2. Pseudocode and Flowcharts | 伪代码与流程图

Pseudocode is a simplified, human-readable way of writing algorithms using common keywords such as INPUT, OUTPUT, IF, THEN, ELSE, WHILE and ENDWHILE. It is not tied to any specific programming language, so exam answers can focus on logic rather than syntax.

伪代码是一种简化的、易读的算法书写方式，使用常见关键字，如 INPUT、OUTPUT、IF、THEN、ELSE、WHILE 和 ENDWHILE。它不依赖于任何特定编程语言，因此考试答案可以关注逻辑而非语法。

A flowchart shows the same algorithm visually. Standard symbols include a rounded rectangle for START/STOP, a parallelogram for input/output, a rectangle for a process, a diamond for a decision and arrows for flow direction. You should be able to convert between pseudocode and a flowchart.

流程图以可视化方式显示同一算法。标准符号包括：圆角矩形表示开始/结束，平行四边形表示输入/输出，矩形表示处理，菱形表示判断，箭头表示流程方向。你应能在伪代码和流程图之间进行转换。

3. Programming Basics: Variables and Data Types | 编程基础：变量与数据类型

A variable is a named storage location in memory that can hold a value which may change while a program runs. For example, score ← 0 stores the value 0 in the variable called score. Constants are similar, but their value does not change after being set.

变量是内存中命名的存储位置，可保存程序运行时可能改变的值。例如，score ← 0 将值 0 存储到名为 score 的变量中。常量类似，但其值在设置后不会改变。

Common data types include INTEGER, REAL or FLOAT, CHAR, STRING and BO

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