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知识点总结

Programming Paradigms — 编程范式​

Low-Level (Assembly) — 低级语言（汇编）​

  • Addressing modes:
    • Immediate — 立即寻址: operand is the actual value (e.g. MOV R1, #42)
    • Direct — 直接寻址: operand is a memory address (e.g. MOV R1, 2000)
    • Indirect — 间接寻址: operand is a memory address that holds the target address (e.g. MOV R1, (2000))
    • Indexed — 变址寻址: address = base + index register (e.g. MOV R1, 2000(R2))
    • Relative — 相对寻址: address = current PC + offset (used for branching)

Imperative / Procedural — 命令式 / 过程式​

  • Uses variables, sequence (statements execute in order), selection (IF/ELSE), iteration (loops)
  • Organised into procedures and functions
  • Procedure: performs an action (may not return a value)
  • Function: computes and returns a value
  • Top-down design: break problems into smaller sub-procedures

Object-Oriented (OOP) — 面向对象​

  • Class — 类: blueprint / template for objects
  • Object — 对象: instance of a class
  • Encapsulation — 封装: bundling data + methods, hiding internal state via private/public
  • Inheritance — 继承: a class derives properties and methods from a parent class
  • Polymorphism — 多态: same interface, different implementations (method overriding / overloading)
  • Containment / Composition — 组合: one class contains an instance of another as a field

Declarative — 声明式​

  • Describes what to achieve, not how (logic programming)
  • Facts — 事实: statements that are unconditionally true (e.g. parent(john, mary).)
  • Rules — 规则: conditional statements (e.g. grandparent(X, Z) :- parent(X, Y), parent(Y, Z).)
  • Queries — 查询: questions asked of the system (e.g. ?- grandparent(john, Who).)
  • Backward chaining — 反向链: starts from the goal/query and works backward, matching rules and facts to find a solution (Prolog-style inference)
...

Backward chaining is goal-driven — it starts with the conclusion and searches for supporting evidence.

RPN (Reverse Polish Notation) — 逆波兰表示法​

  • Also called postfix notation — 后缀表示法
  • Operator follows its operands (e.g. 3 4 + instead of 3 + 4)
  • No brackets needed — order of operations is unambiguous
  • Evaluated using a stack:
    1. Read tokens left to right
    2. If operand → push onto stack
    3. If operator → pop required number of operands, apply operator, push result back
  • Examples:
    • Infix: (3 + 4) × 5 → RPN: 3 4 + 5 ×
    • Infix: 3 + 4 × 5 → RPN: 3 4 5 × +
...

Always pay attention to the order of operands when popping from the stack — subtraction and division are not commutative.

File Processing — 文件处理​

  • OPENFILE: opens a file for reading/writing/appending
  • READFILE: reads data from an open file
  • WRITEFILE: writes data to an open file
  • CLOSEFILE: closes the file and releases resources
  • File modes:
    • Read — 读取: file must already exist
    • Write — 写入: creates new file or overwrites existing
    • Append — 追加: adds data to end of existing file
  • Access methods:
    • Serial — 串行: data stored/read in order (e.g. tape)
    • Sequential — 顺序: records accessed one after another from start
    • Random / Direct — 随机 / 直接: access any record directly using its address/key

Exception Handling — 异常处理​

  • Mechanism to handle runtime errors gracefully without crashing the program
  • Structure: TRY...EXCEPT (or TRY...CATCH in some languages)
  • Common exception types:
    • IOError: input/output operation failure (e.g. file not found, disk full)
    • ValueError: operation receives an argument of correct type but invalid value
    • IndexError: accessing an index outside the bounds of a sequence
    • KeyError: accessing a non-existent key in a dictionary
    • TypeError: operation applied to object of inappropriate type
  • Use exceptions when:
    • The error is unpredictable (e.g. network failure, missing file)
    • The normal flow of logic should not be cluttered with error-checking code
    • The error must propagate up the call stack
...

Do not use exceptions for normal control flow — they should be reserved for genuinely exceptional conditions.