Programming Fundamentals: Data Types, Variables and Control Structures | 编程基础：数据类型、变量与控制结构

📚 Programming Fundamentals: Data Types, Variables and Control Structures | 编程基础：数据类型、变量与控制结构

In Edexcel A-Level Computer Science, the programming paper tests your ability to design, write and trace algorithms using a clear pseudocode style. This article covers the core programming building blocks: data types, variables, constants, operators, selection, iteration, arrays, strings and subprograms.

在 Edexcel A-Level 计算机科学考试中，编程部分考查你使用清晰的伪代码风格设计、编写和跟踪算法的能力。本文涵盖核心编程构建模块：数据类型、变量、常量、运算符、选择结构、迭代、数组、字符串和子程序。

1. Programming and Pseudocode | 编程与伪代码

Programming is the process of creating a set of instructions that a computer can execute to solve a problem. In Edexcel exams, you are expected to express algorithms in a standard pseudocode syntax rather than a specific programming language.

编程是创建一组计算机能够执行以解决问题的指令的过程。在 Edexcel 考试中，你需要使用标准伪代码语法来表达算法，而不是某种特定编程语言。

Pseudocode should be clear, unambiguous and consistent. Common Edexcel conventions include INPUT for input, OUTPUT for output, ← for assignment, and keywords such as IF, WHILE, FOR and ENDIF.

伪代码应清晰、无歧义且一致。常见的 Edexcel 规范包括：用 INPUT 表示输入，OUTPUT 表示输出，← 表示赋值，以及 IF、WHILE、FOR 和 ENDIF 等关键字。

OUTPUT “Enter age”

This simple statement displays a message. You can include it as part of an algorithm.

这个简单语句用于显示一条消息。你可以将其作为算法的一部分。

2. Variables, Constants and Assignment | 变量、常量与赋值

A variable is a named storage location whose value can change while a program is running. A constant is a named value that cannot be changed after it is assigned.

变量是一个命名的存储位置，其值在程序运行期间可以改变。常量是一个命名的值，在赋值之后不能改变。

Assignment stores a value in a variable. In Edexcel pseudocode, the left arrow ← is used: score ← 0. This means ‘set the variable score to 0’.

赋值将值存储到变量中。在 Edexcel 伪代码中，使用左箭头 ←：score ← 0。这表示“将变量 score 设置为 0”。

Constants are often written in upper case, for example MAX_ITEMS ← 100. They improve readability and prevent accidental changes.

常量通常使用大写字母书写，例如 MAX_ITEMS ← 100。它们可以提高可读性并防止意外修改。

3. Primitive Data Types | 原始数据类型

Edexcel pseudocode recognises several primitive data types. Choosing the correct type affects how data is stored and what operations are valid.

Edexcel 伪代码识别几种原始数据类型。选择正确的类型会影响数据的存储方式以及合法的操作。