Mastering Operators and Expressions in Edexcel A-Level Programming | 精通 Edexcel A-Level 编程中的运算符与表达式

📚 Mastering Operators and Expressions in Edexcel A-Level Programming | 精通 Edexcel A-Level 编程中的运算符与表达式

Every Edexcel A-Level programming question eventually comes down to evaluating expressions: predicting what a line of code does, writing a condition for an if statement, or tracing a loop until a variable changes. This revision guide focuses on operators and expressions, using Python-style syntax alongside the Edexcel pseudocode conventions you are likely to meet in Paper 2.

每一道 Edexcel A-Level 编程题最终都会回到表达式求值：预测某行代码的运行结果、为 if 语句写出条件，或者追踪循环直到变量发生变化。本复习指南聚焦运算符与表达式，使用 Python 风格语法，并结合你在 Paper 2 中可能遇到的 Edexcel 伪代码规范。

1. Operators and Expressions: Core Concepts | 运算符与表达式：核心概念

An operator is a symbol that tells the computer to perform a specific operation on one or more operands. An expression is any valid combination of values, variables, operators and function calls that can be evaluated to produce a single value.

运算符是告诉计算机对一个或多个操作数执行特定操作的符号。表达式是值、变量、运算符和函数调用的任意合法组合，能够被求值并产生一个单一的值。

For example, in total = price * quantity + 10, the expression price * quantity + 10 is evaluated first and then assigned to the variable total. This distinction between expression evaluation and assignment is important in trace tables and written answers.

例如，在 total = price * quantity + 10 中，先计算表达式 price * quantity + 10，再把结果赋给变量 total。表达式求值与赋值之间的区别在跟踪表和书面答案中十分重要。

expression → evaluated to a single value → assigned or used in a statement

表达式 → 求值为单一值 → 赋给变量或用于语句

2. Arithmetic Operators | 算术运算符

The arithmetic operators perform basic mathematical calculations. Edexcel questions often expect you to know both the exact division operator and the integer-division operator, because they behave differently in Python and in pseudocode.

算术运算符执行基本数学计算。Edexcel 题目经常要求你同时掌握精确除法运算符和整数除法运算符，因为它们在 Python 和伪代码中的行为不同。

Key arithmetic operators are summarised below. The result column assumes a = 7 and

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