Pseudocode Examples & Sample Algorithms — IGCSE & A-Level

1. Basics — Input & Output

Every algorithm starts with getting data in and displaying data out. These examples show the fundamental pseudocode structure.

Hello World & User Greeting Easy

DECLARE Name : STRING
OUTPUT "What is your name?"
INPUT Name
OUTPUT "Hello, ", Name, "! Welcome to PseudoStudio."

Simple Calculator (Add Two Numbers) Easy

DECLARE Num1, Num2, Total : REAL

OUTPUT "Enter first number:"
INPUT Num1
OUTPUT "Enter second number:"
INPUT Num2

Total ← Num1 + Num2
OUTPUT "The sum is: ", Total

2. Conditional Statements

These examples demonstrate IF-THEN-ELSE and CASE OF selection structures — common in both Paper 1 and Paper 2.

Grade Calculator (IF...ELSE) Easy

DECLARE Score : INTEGER
OUTPUT "Enter exam score (0-100):"
INPUT Score

IF Score >= 70
    THEN
        OUTPUT "Grade: A"
    ELSE
        IF Score >= 55
            THEN
                OUTPUT "Grade: B"
            ELSE
                IF Score >= 40
                    THEN
                        OUTPUT "Grade: C"
                    ELSE
                        OUTPUT "Grade: U (Ungraded)"
                ENDIF
        ENDIF
ENDIF

3. Loops (FOR, WHILE, REPEAT)

Times Table Generator (FOR Loop) Easy

DECLARE n, i : INTEGER
OUTPUT "Enter a number for its times table:"
INPUT n

FOR i ← 1 TO 12
    OUTPUT n, " x ", i, " = ", n * i
NEXT i

Input Validation (REPEAT UNTIL) Medium

DECLARE Age : INTEGER

// REPEAT UNTIL guarantees at least one execution
REPEAT
    OUTPUT "Enter your age (1 to 120):"
    INPUT Age
    IF Age < 1 OR Age > 120
        THEN OUTPUT "Invalid! Please try again."
    ENDIF
UNTIL Age >= 1 AND Age <= 120

OUTPUT "Age accepted: ", Age

Running Total with WHILE Loop Medium

DECLARE Num, Total : INTEGER
Total ← 0
OUTPUT "Enter numbers (enter -1 to stop):"

INPUT Num
WHILE Num <> -1
    Total ← Total + Num
    INPUT Num
ENDWHILE

OUTPUT "Running total: ", Total

4. Arrays (1D & 2D)

Find Maximum in 1D Array Medium

DECLARE Scores[1:5] : INTEGER
DECLARE i, Max : INTEGER

// Fill array with user input
FOR i ← 1 TO 5
    OUTPUT "Enter score ", i, ":"
    INPUT Scores[i]
NEXT i

// Find the maximum value
Max ← Scores[1]
FOR i ← 2 TO 5
    IF Scores[i] > Max
        THEN Max ← Scores[i]
    ENDIF
NEXT i

OUTPUT "Highest score: ", Max

Bubble Sort Algorithm Hard

DECLARE A[1:5] : INTEGER
DECLARE i, j, Temp : INTEGER

A[1] ← 64
A[2] ← 25
A[3] ← 12
A[4] ← 22
A[5] ← 11

FOR i ← 1 TO 4
    FOR j ← 1 TO 5 - i
        IF A[j] > A[j+1]
            THEN
                Temp ← A[j]
                A[j] ← A[j+1]
                A[j+1] ← Temp
        ENDIF
    NEXT j
NEXT i

OUTPUT "Sorted array:"
FOR i ← 1 TO 5
    OUTPUT A[i]
NEXT i

5. Functions & Procedures

Factorial Function Hard

FUNCTION Factorial(n : INTEGER) RETURNS INTEGER
    DECLARE Result, i : INTEGER
    Result ← 1
    FOR i ← 1 TO n
        Result ← Result * i
    NEXT i
    RETURN Result
ENDFUNCTION

DECLARE Num, Answer : INTEGER
OUTPUT "Enter a number to find its factorial:"
INPUT Num
Answer ← Factorial(Num)
OUTPUT Num, "! = ", Answer

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