Operators and Expressions in Programming | 编程中的运算符与表达式

📚 Operators and Expressions in Programming | 编程中的运算符与表达式

Operators are fundamental symbols in programming that allow us to perform operations on data. In the Edexcel A-level Computer Science curriculum, a solid understanding of operators and expressions is essential for writing efficient algorithms, tracing pseudocode, and solving computational problems. This article covers arithmetic, relational, logical, bitwise, and assignment operators, together with operator precedence, type conversion, and common pitfalls.

运算符是编程中基本的符号，用于对数据执行各种操作。在 Edexcel A-level 计算机科学课程中，透彻理解运算符与表达式对于编写高效算法、跟踪伪代码以及解决计算问题至关重要。本文将涵盖算术运算符、关系运算符、逻辑运算符、位运算符和赋值运算符，同时讨论运算优先级、类型转换和常见误区。

1. Arithmetic Operators | 算术运算符

Arithmetic operators perform mathematical calculations. In Edexcel pseudocode and most high-level languages, the standard arithmetic operators include addition (+), subtraction (-), multiplication (*), division (/), integer division (DIV), modulus (MOD), and exponentiation (^). For example, the expression 7 + 3 * 2 evaluates to 13 due to precedence. Integer division, such as 10 DIV 3, yields 3, discarding any remainder, while 10 MOD 3 gives 1. The exponentiation operator (^) raises a number to a power: 2^3 equals 8. These operators follow typical mathematical rules, but careful attention must be paid to integer vs. floating-point division when precision is required.

算术运算符执行数学计算。在 Edexcel 伪代码和大多数高级语言中，标准算术运算符包括加号 (+)、减号 (-)、乘号 (*)、除号 (/)、整除 (DIV)、取模 (MOD) 和指数 (^)。例如，表达式 7 + 3 * 2 因优先级结果为 13。整除运算如 10 DIV 3 结果为 3，舍去余数；而 10 MOD 3 结果为 1。指数运算符 (^) 计算幂次：2^3 等于 8。这些运算符遵循常规数学规则，但在需要精度时必须注意整除与浮点除法的区别。

2. Relational (Comparison) Operators | 关系（比较）运算符

Relational operators compare two values and return a Boolean result (TRUE or FALSE). The standard set in Edexcel pseudocode includes: equal to (=), not equal to (<>), less than (<), greater than (>), less than or equal to (<=), and greater than or equal to (>=). For instance, the condition score >= 70 evaluates to TRUE if score is 85. These operators are essential for decision making and loop control. Note that while assignment also uses the ‘=’ symbol, context distinguishes assignment from comparison. In Python, equality uses ‘==’, and ‘!=’ replaces ‘<>’, but the Edexcel pseudocode simplifies with a single ‘=’ for both assignment and equality – the meaning is deduced from the surrounding statement.

关系运算符比较两个值并返回布尔结果（TRUE 或 FALSE）。Edexcel 伪代码中的标准关系运算符包括：等于 (=)、不等于 (<>)、小于 (<)、大于 (>)、小于等于 (<=) 和大于等于 (>=)。例如，条件

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