Pseudocode Foundations & Conventions: Variables, Constants And Identifiers In Pseudocode (Copy)

Variables, Constants And Identifiers In Pseudocode

Role Of Variables, Constants And Identifiers

• They define what data is stored, how it is accessed, and how logic is understood
• Examiner checks:
  • Correct declaration
  • Correct naming
  • Correct usage throughout the algorithm
• Poor identifier usage causes:
  • Ambiguity
  • Tracing difficulty
  • Loss of easy structure marks

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Variables (Changeable Data Storage)

Aspect	Correct Practice
Must be declared	Before use
Must be initialised	Before processing
Meaningful name	Describes purpose
Correct data type	Matches stored value

Variable Declaration Format

DECLARE Age : INTEGER
DECLARE Name : STRING
DECLARE Average : REAL
DECLARE Found : BOOLEAN

Variable Initialisation Examples

Age ← 0
Name ← ""
Average ← 0
Found ← FALSE

• Variables can change during execution
• Initialisation prevents undefined behaviour

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Common Variable Types (AS Level Scope)

Data Type	Used For	Example
INTEGER	Whole numbers	Count, Age
REAL	Decimal numbers	Average, Price
STRING	Text	Name, Address
BOOLEAN	True / False	Found, Valid
CHAR	Single character	Grade

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Variable Naming Rules (Examiner-Friendly)

Poor Name	Problem	Correct Name
x	No meaning	TotalMarks
a1	Unclear	StudentAge
t	Ambiguous	Total
flag	Vague	Found

• Names must describe purpose, not data type
• Examiner should understand meaning instantly

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

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Constants (Fixed Values)

Feature	Rule
Value never changes	Must remain constant
Declared once	At start
Named clearly	Uppercase recommended

Constant Declaration

CONSTANT PassMark ← 50
CONSTANT MaxStudents ← 30

Using Constants In Logic

IF Score >= PassMark THEN
    OUTPUT "Pass"
ENDIF

• Improves readability
• Avoids “magic numbers”

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Constants Vs Variables

Feature	Variable	Constant
Value changes	Yes	No
Assignment allowed	Yes	No
Purpose	Temporary storage	Fixed reference

• Never reassign a constant
• Using constants improves exam clarity

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Identifier Rules (What Counts As An Identifier)

• Identifiers include:
  • Variable names
  • Constant names
  • Procedure names
  • Function names
  • Array names
  • Record field names

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Identifier Naming Conventions

Identifier Type	Naming Style	Example
Variable	Descriptive noun	TotalMarks
Constant	Uppercase	PASSMARK
Procedure	Verb-based	DisplayResult
Function	Verb / Get…	GetAverage
Boolean	Yes/No meaning	Found, Valid

• Avoid single-letter identifiers
• Avoid names that look like keywords

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

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Identifier Consistency (Critical For Tracing)

Bad Practice	Problem
Using Total and total	Case confusion
Using Marks and Mark	Logical ambiguity
Renaming mid-program	Tracing error

Correct Consistent Usage

DECLARE TotalMarks : INTEGER
TotalMarks ← 0
TotalMarks ← TotalMarks + Score

• Same spelling
• Same capitalisation
• Same meaning throughout

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Declaring Multiple Variables Clearly

Poor Practice

DECLARE A, B, C : INTEGER

Examiner-Friendly

DECLARE Count : INTEGER
DECLARE Total : INTEGER
DECLARE Score : INTEGER

• Easier to trace
• Easier to award marks

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Variables In Expressions

Average ← Total / Count

• Left side: single variable
• Right side: expression
• Expression may include:
  • Variables
  • Constants
  • Operators

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Boolean Variables (Flags)

Purpose	Example
Control loop exit	Found
Track conditions	Valid

Found ← FALSE

IF Value = Target THEN
    Found ← TRUE
ENDIF

• Flags must always be initialised
• Flags improve loop control clarity

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

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Variables In Loops

Counter Variable

Count ← 0

WHILE Count < 5 DO
    INPUT Value
    Count ← Count + 1
ENDWHILE

Accumulator Variable

Total ← 0

FOR i ← 1 TO 10
    Total ← Total + Marks[i]
ENDFOR

• Counter controls repetition
• Accumulator stores running total

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Variables With Arrays

DECLARE Marks : ARRAY[1:10] OF INTEGER

• Array name is an identifier
• Index must be an INTEGER variable

FOR i ← 1 TO 10
    OUTPUT Marks[i]
ENDFOR

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Variables With Records

RECORD StudentType
    Name : STRING
    Age : INTEGER
    Score : INTEGER
ENDRECORD

DECLARE Student : StudentType
Student.Score ← 85

• Record fields are identifiers
• Field access must be explicit

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Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change AS Level Computer Science Full Scale Course

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Reserved Words (Identifiers Must Avoid These)

• IF, THEN, ELSE, ENDIF
• FOR, TO, ENDFOR
• WHILE, DO, ENDWHILE
• PROCEDURE, FUNCTION, RETURN
• INPUT, OUTPUT

Incorrect Identifier	Why Wrong
DECLARE IF : INTEGER	Keyword
DECLARE FOR : INTEGER	Keyword

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Examiner Traps And Safe Practices

Trap	Fix
Uninitialised variable	Initialise immediately
Confusing variable names	Use descriptive names
Reassigning constants	Never assign again
Mixed identifier styles	Stay consistent
Over-short names	Expand for clarity

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Examiner-Safe Declaration Template

DECLARE Count : INTEGER
DECLARE Total : INTEGER
DECLARE Average : REAL
DECLARE Found : BOOLEAN

Count ← 0
Total ← 0
Average ← 0
Found ← FALSE

• Clean
• Traceable
• Examiner-approved