Pseudo code 伪代码

1. What Is Pseudocode?

Pseudocode is a high-level, language-independent description of an algorithm.
It looks like code, but it is not tied to any programming language.
Its purpose is to help you think and design before writing real code.

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2. Basic Principles of Pseudocode

• Use plain English to describe logic.

• Focus on steps, not syntax.

• Be clear, structured, and consistent.

• Indentation represents blocks (like loops or conditionals).

• No need to worry about real coding rules (types, semicolons, etc.).

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3. Common Keywords

These are commonly used in pseudocode across textbooks:

Purpose	Keyword Examples
Start/End	BEGIN, END
Variables	SET, LET, INITIALIZE
Conditions	IF, ELSE, ELSE IF, END IF
Loops	FOR, WHILE, REPEAT…UNTIL, END FOR
Functions	FUNCTION, RETURN
I/O	READ, WRITE, PRINT

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4. Basic Structures

4.1 Sequential Execution

BEGIN PRINT "Hello" SET x ← 10 SET y ← x + 5 PRINT y END

4.2 Conditional Branching

IF score ≥ 60 THEN PRINT "Pass" ELSE PRINT "Fail" END IF

4.3 Looping

FOR loop

FOR i ← 1 TO 10 DO PRINT i END FOR

WHILE loop

WHILE n > 0 DO PRINT n n ← n - 1 END WHILE

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5. Functions

FUNCTION Add(a, b) RETURN a + b END FUNCTION

Calling a function:

result ← Add(3, 4) PRINT result

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6. A Complete Example: Find Maximum in an Array

FUNCTION FindMax(arr, n) SET max ← arr[0] FOR i ← 1 TO n - 1 DO IF arr[i] > max THEN max ← arr[i] END IF END FOR RETURN max END FUNCTION

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7. Tips for Writing Good Pseudocode

• Use meaningful names (e.g., total, count, isFound).

• Keep it language-neutral (not C, not Python, just logic).

• Make sure each step is unambiguous.

• Add comments if needed.

• Aim for readability over accuracy.