11.1 Programming Basics 编程基础简答

Scope

本页只整理 basic operations、operators、expressions 和 built-in functions 的理解与错误解释。完整 pseudocode implementation 留到专项。

Basic programming operations

• Declaration：introduces an identifier and its data type。
• Initialisation：assigns a starting value before use。
• Assignment：stores the evaluated right-hand value in an identifier。
• Input/output：receives data or presents/writes a result。
• Expression：combines values, identifiers, functions and operators to produce one value。

Type compatibility

Expression and assignment must use compatible types：

• Arithmetic operators require numeric operands。
• & concatenates CHAR/STRING values；it is not numeric addition。
• Logical operators AND/OR/NOT require Boolean operands/results。
• Comparisons produce BOOLEAN。
• A STRING cannot be added numerically to an INTEGER without conversion。

Error explanation pattern

不要只写 “wrong operator”。写明 required type 和 actual type：

INT(x / 2) returns an INTEGER, so it cannot be used as a Boolean operand with AND.

Built-in functions

Built-in/library routines perform common operations that do not need to be rewritten。考试会提供未在 pseudocode guide 中规定的 functions。

理解 function expression 时依次检查：

• Number and type of parameters。
• Return data type。
• Index/position conventions for string extraction。
• Whether explicit conversion is needed。

常见 categories：string length/extraction/case conversion；numeric conversion/rounding；character-code conversion；date day/month/year；random values。

Evaluating expressions

• Work from inner function calls outward。
• Record the data type after each operation。
• Apply arithmetic precedence and brackets。
• For Boolean expressions, evaluate comparisons before AND/OR/NOT as defined。
• Keep quotation marks conceptually: "12" is STRING, while 12 is INTEGER。

Describing an algorithm without code

需要 detailed description 时仍应包含 variables、initial values、input loop、conditions、updates and final output。用自然语言顺序描述，不写 pseudocode keywords when prohibited。

Exam checklist

• Assignment 与 comparison 是否区分？
• Operator operands 是否类型匹配？
• Function parameter 与 return type 是否匹配？
• 字符串连接是否使用 string operation，而不是 arithmetic？
• Explain error 是否写清 expected/actual type？

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Declaration、assignment、function calls 和完整 algorithm pseudocode 将在代码专项中练习。