Cost And Management Accounting Formats (AS Level): Marginal Costing Contribution Statement Format (Copy)

Nested Selection Logic With Worked Examples

Purpose Of Nested Selection

• Nested selection is used when:
  • One decision depends on the result of another
  • Conditions are hierarchical, not independent
• Examiner checks:
  • Logical dependency
  • Correct nesting and indentation
  • Correct ENDIF matching

What Nested Selection Means

• An IF statement inside another IF or ELSE
• Inner condition is evaluated only if outer condition allows it
• Used when:
  • Access control
  • Validation steps
  • Tiered decision-making

Basic Nested IF Structure

IF condition1 THEN
    IF condition2 THEN
        statements
    ELSE
        statements
    ENDIF
ELSE
    statements
ENDIF

• Inner IF only runs when outer IF condition is TRUE
• Each IF must have its own ENDIF

Worked Example 1: Age And ID Check

IF Age >= 18 THEN
    IF HasID = TRUE THEN
        OUTPUT "Access Granted"
    ELSE
        OUTPUT "ID Required"
    ENDIF
ELSE
    OUTPUT "Underage"
ENDIF

Execution Logic

• If Age < 18 → “Underage”
• If Age ≥ 18 AND HasID = TRUE → “Access Granted”
• If Age ≥ 18 AND HasID = FALSE → “ID Required”

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

Worked Example 2: Login Validation System

IF Locked = FALSE THEN
    IF Username = "Admin" THEN
        IF Password = "1234" THEN
            OUTPUT "Login Successful"
        ELSE
            OUTPUT "Incorrect Password"
        ENDIF
    ELSE
        OUTPUT "Unknown User"
    ENDIF
ELSE
    OUTPUT "Account Locked"
ENDIF

Why Nested IF Is Correct Here

• Password check only makes sense if:
  • Account is not locked
  • Username is correct
• Prevents unnecessary checks

Nested IF Vs ELSE IF (Critical Distinction)

Worked Example 3: Exam Entry Eligibility

IF FeePaid = TRUE THEN
    IF Attendance >= 75 THEN
        OUTPUT "Eligible For Exam"
    ELSE
        OUTPUT "Attendance Short"
    ENDIF
ELSE
    OUTPUT "Fee Not Paid"
ENDIF

• Attendance only checked if fee is paid
• Logical dependency clearly shown

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

Deep Nesting (Three-Level Example)

IF Age >= 18 THEN
    IF HasTicket = TRUE THEN
        IF HasSeat = TRUE THEN
            OUTPUT "Entry Allowed"
        ELSE
            OUTPUT "Seat Not Assigned"
        ENDIF
    ELSE
        OUTPUT "Ticket Required"
    ENDIF
ELSE
    OUTPUT "Age Restriction"
ENDIF

Execution Flow

• Age < 18 → Stop immediately
• Age ≥ 18 → Check ticket
• Ticket present → Check seat
• Seat present → Entry allowed

Indentation Rules (Examiner Focus)

Nested IF Inside ELSE Block

IF Score >= 50 THEN
    OUTPUT "Pass"
ELSE
    IF Score >= 40 THEN
        OUTPUT "Compartment"
    ELSE
        OUTPUT "Fail"
    ENDIF
ENDIF

• ELSE can contain another IF
• Common grading adjustment logic

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

Nested Selection Inside Loops (Very Common)

FOR i ← 1 TO 5
    IF Marks[i] >= 50 THEN
        IF Marks[i] >= 80 THEN
            OUTPUT "Distinction"
        ELSE
            OUTPUT "Pass"
        ENDIF
    ELSE
        OUTPUT "Fail"
    ENDIF
ENDFOR

Simplifying Nested Logic (When Possible)

Over-Nested (Avoid)

IF A = TRUE THEN
    IF B = TRUE THEN
        OUTPUT "Yes"
    ENDIF
ENDIF

Cleaner (Same Logic)

IF A = TRUE AND B = TRUE THEN
    OUTPUT "Yes"
ENDIF

• Only simplify if dependency is not required
• Examiner prefers clarity over cleverness

Common Student Mistakes In Nested Selection

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

Examiner-Safe Nested Selection Template

IF outerCondition THEN
    IF innerCondition THEN
        statements
    ELSE
        statements
    ENDIF
ELSE
    statements
ENDIF

• Clear dependency
• Easy to trace
• Maximum structure marks secured