What are the basic programming concepts covered in the Cambridge IGCSE Computer Science syllabus?

The Cambridge IGCSE Computer Science syllabus covers fundamental programming concepts such as variables, data types, operators, control structures (like loops and conditionals), functions, and arrays. These concepts form the foundation for understanding how to write and analyze simple programs.

How do variables and data types function in programming?

In programming, variables are used to store data that can be manipulated by the program. Each variable has a data type that defines the kind of data it can hold, such as integers, floats, or strings. Understanding variables and data types is crucial for managing data effectively in any programming language.

What is the importance of control structures in programming?

Control structures, such as loops and conditionals, are essential in programming because they allow the flow of the program to change based on certain conditions. This enables programmers to execute code repeatedly (using loops) or make decisions (using conditionals), which is vital for creating dynamic and responsive programs.

Can you explain the concept of functions in programming?

Functions are reusable blocks of code that perform a specific task. They help in organizing code, making it more readable and maintainable. By using functions, programmers can avoid redundancy, as the same function can be called multiple times with different inputs to produce different outputs.

What role do arrays play in programming?

Arrays are data structures that store multiple values of the same data type in a single variable. They are useful for managing collections of data, such as lists of numbers or strings. Arrays allow programmers to efficiently access and manipulate large sets of data using indexing.

Why is "Using a variable for something that should be a constant" a common mistake in Programming Concepts?

Why it happens: Students declare everything as a variable. How to avoid it: If the value WON'T change (π, VAT rate at the time of the program, max users), use a CONSTANT. Documents intent and prevents accidental modification. Source: 0478 Examiner Reports 2022-2024

Why is "Using Integer for prices" a common mistake in Programming Concepts?

Why it happens: Prices look like 'whole numbers'. How to avoid it: Prices have pence/cents — use REAL (or a dedicated Currency/Decimal type). Integer prices lose accuracy on calculations.

Why is "Calling a procedure a function (or vice versa)" a common mistake in Programming Concepts?

Why it happens: Both are 'subroutines'. How to avoid it: Function RETURNS a value. Procedure does NOT return a value. The distinction is exactly that one rule.

Why is "Making every variable global" a common mistake in Programming Concepts?

Why it happens: Globals are accessible everywhere; feels easier. How to avoid it: Overuse of globals leads to spaghetti code and bugs from unintended side effects. Default to LOCAL; promote to global only when truly needed.

Cambridge IGCSE Computer Science (0478)

Programming Concepts

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Short Notes - Programming Concepts

Detailed Study Notes

Detailed notes on Programming for Cambridge IGCSE Computer Science, covering key concepts, explanations, examples, and exam-focused revision points.

Programming Concepts Study Notes — Cambridge IGCSE Computer Science 0478 (2026-2028 syllabus)

The building blocks of every program. Variables, constants and the standard data types. Operators, expressions, the three control structures. Subroutines (procedures and functions), parameters, scope (local vs global), and string-manipulation functions.

At a glance

Variable can change; constant cannot.
Six common data types: integer, real, boolean, string, char, date.
Three control structures: sequence, selection, iteration.
Procedure returns nothing; function returns a value.
Parameter = receives an argument's value.
Local scope = inside subroutine; global = everywhere.
Default to LOCAL — easier to reason about.
String functions — LENGTH, SUBSTRING, CONCAT (Cambridge pseudocode).

What you’ll learn

Mapped to the Cambridge IGCSE 0478 syllabus (2026-2028).

1.22.1 — Distinguish variables and constants.
1.22.2 — Identify common data types and their use.
1.22.3 — Use the three control structures.
1.22.4 — Use procedures and functions; pass parameters.
1.22.5 — Distinguish local and global variables.
1.22.6 — Use string-manipulation functions.

Variables and constants

Storage with a name. Variable can change; constant cannot.

A variable is a named storage location whose value CAN CHANGE while the program runs. Use for things that may take different values over time — user input, counters, totals, current state.

A constant is a named storage location whose value DOES NOT CHANGE after it's set. Use for fixed values:

Mathematical constants (π = 3.14159...).
Configuration limits (MAX_USERS = 100, VAT_RATE = 0.20).
Magic numbers (DAYS_IN_WEEK = 7) — replacing them with named constants makes code self-documenting.

Why prefer constants when possible.

Self-documenting (circumference ← 2 * PI * radius reads better than circumference ← 2 * 3.14159 * radius).
Single source of truth — change in one place if the value updates.
Compiler / interpreter can prevent accidental modification.

Cambridge tip. Mark scheme expects the precise distinction: variable = changeable, constant = fixed. Don't say 'constants are like variables but...'.

Variable: value changes.
Constant: value stays fixed.
Constants are self-documenting and safer.

Common data types

Six types you'll see on every paper.

Cambridge tests these data types:

Type	Stores	Example
Integer	Whole numbers	-3, 0, 42
Real (Float)	Numbers with decimals	3.14, -0.5
Boolean	TRUE / FALSE	TRUE
String	Sequence of characters	"Hello"
Char	Single character	'A'
Date	Date / DateTime	09/05/2026

Choose the right type.

Counter / age / quantity → integer.
Price / measurement / scientific value → real.
Yes/no / on/off / true/false → boolean.
Names / addresses / messages → string.
Single grade letter / single character flag → char (or string of length 1).
Birthdays / timestamps → date / datetime.

Three families: numeric (integer and real), boolean (true/false), textual (char and string). Plus date for calendar values.

Cambridge tip. Match the type to the SCENARIO. Using integer for prices loses pence; using string for ages prevents arithmetic.

Six common types — know each.
Real (not integer) for prices.
Boolean for yes/no flags.

See the full worked example for programming concepts →

Procedures and functions

Reusable blocks. Procedure does; function returns.

A subroutine is a self-contained block of code that does a task. Two kinds:

Procedure. Does a task; does NOT return a value.

PROCEDURE DisplayMenu()
  OUTPUT "1. Add"
  OUTPUT "2. Remove"
  OUTPUT "3. Quit"
ENDPROCEDURE

Called: CALL DisplayMenu().

Function. Does a task; RETURNS a value to the caller.

FUNCTION AreaOfCircle(radius : REAL) RETURNS REAL
  RETURN 3.14159 * radius * radius
ENDFUNCTION

Called: area ← AreaOfCircle(5).

Both share:

They take parameters (variables that receive values from the caller).
They have local variables (private to the subroutine).
They can be called from many places — write once, use many times.

Why use subroutines.

Reuse — write once, call from many places.
Less duplication — no copy-pasted code drifting out of sync.
Easier to test — test each subroutine in isolation.
Modular — top-level code reads as a sequence of named operations.

Cambridge tip. When asked to distinguish, the SINGLE rule is: function returns a value, procedure does not.

Procedure does; function returns.
Both take parameters and have local scope.
Subroutines enable reuse, less duplication, easier testing.

See the full worked example for programming concepts →

Local vs global scope

Where can you SEE the variable?

A variable's scope is the part of the program where it's accessible.

Local variables. Declared INSIDE a subroutine; only accessible within that subroutine. Created when the subroutine is called and destroyed when it ends.

Global variables. Declared OUTSIDE all subroutines; accessible EVERYWHERE in the program. Persists for the program's lifetime.

Why prefer local.

Encapsulation — one subroutine can't accidentally change another's variables.
Easier debugging — variable changes localised.
Less memory — local variables are reclaimed when the subroutine ends.
Reuse — subroutines work on parameters and locals; can be lifted between programs.

When global IS appropriate.

Configuration values needed everywhere (often defined as CONSTANTS, not variables).
A few clearly-named state variables shared across the whole program.

Cambridge tip. Mark scheme expects the distinction (where declared / where visible) AND a stated advantage of local (one of: encapsulation, debugging, memory, reuse).

Local: inside subroutine; created/destroyed with it.
Global: outside all subroutines; everywhere; persistent.
Default to local for safety.

See the full worked example for programming concepts →

String-manipulation functions

LENGTH, SUBSTRING, UCASE, LCASE — Cambridge pseudocode standards.

Strings are sequences of characters; Cambridge has a small set of built-in functions for manipulating them.

LENGTH(text). Returns the number of characters.

LENGTH("Hello")  → 5

SUBSTRING(text, start, length). Returns a slice of the string.

SUBSTRING("Computer", 1, 4)  → "Comp"
SUBSTRING("Computer", 5, 4)  → "uter"

UCASE(text). Convert to uppercase.

UCASE("hello")  → "HELLO"

LCASE(text). Convert to lowercase.

LCASE("WORLD")  → "world"

Concatenation (+). Join strings together.

Greeting ← "Hello, " + Name

Cambridge tip. Use Cambridge pseudocode names (LENGTH, SUBSTRING, UCASE, LCASE) — not Python's len/slice or Java's .length(). Mark schemes deduct for language-specific syntax.

LENGTH, SUBSTRING, UCASE, LCASE — Cambridge standards.
Concatenation with +.
Use Cambridge names, not Python/Java.

Quick recap

Variables change; constants don't.
Six data types — integer, real, boolean, string, char, date.
Procedure does (no return); function returns a value.
Local scope = inside subroutine; global = everywhere; prefer local.
String functions: LENGTH, SUBSTRING, UCASE, LCASE.

Memorise this

Verbatim phrases and definitions Cambridge mark schemes credit.

Variable vs constant — changes vs fixed.
Six data types with one example each.
Procedure = no return. Function = returns a value.
Local vs global scope.
Cambridge string functions: LENGTH, SUBSTRING, UCASE, LCASE.

How it’s examined

Programming concepts appear on every Paper 2. Most-tested questions: identify data types for scenarios (6 marks), distinguish procedure / function (4-6 marks), local vs global (4 marks), string-manipulation pseudocode (6 marks). Examiner reports flag use of language-specific syntax instead of Cambridge pseudocode as the most common loss-of-marks issue.

Sources: Cambridge IGCSE Computer Science 0478 syllabus (2026-2028); 0478 Examiner Reports 2022-2024; 0478/22 Oct/Nov 2024 question paper and mark scheme. Last reviewed 2026-05-09.

Take this whole topic with you

Step-by-step worked examples — Programming Concepts

Step-by-step solutions to past-paper-style questions on programming concepts, written exactly the way a tutor would explain them at the board.

1Choose the correct data type (5 marks) — Getting started
Getting started• Adapted from 0478/22 Oct/Nov 2024 Q4• data-types
Question
Cambridge pseudocode has five core data types: INTEGER, REAL, CHAR, STRING, BOOLEAN. State the most appropriate type for each value: (a) A student's age in whole years. (b) A product's price in pounds and pence. (c) Whether a user is currently logged in. (d) A user's full name. (e) A single letter exam grade.
Step-by-step solution
1. Step 1
  (a) INTEGER (1 mark). Whole number with no decimal part — ages are 0, 1, 2, …
2. Step 2
  (b) REAL (1 mark). A price such as 12.99 has a fractional part, so it must be REAL, not INTEGER.
3. Step 3
  (c) BOOLEAN (1 mark). Only two possible values — TRUE or FALSE.
4. Step 4
  (d) STRING (1 mark). A sequence of characters of arbitrary length used for text.
5. Step 5
  (e) CHAR (1 mark). Exactly one character, e.g. 'A'. A STRING of length 1 would also be accepted but CHAR is the precise choice.
Answer
(a) INTEGER (b) REAL (c) BOOLEAN (d) STRING (e) CHAR. Learn all five 0478 types and the kind of value each holds.
Examiner tip
AO1. Use the EXACT 0478 keyword (INTEGER not 'int', REAL not 'float'). The classic trap is INTEGER for a price — any value with pence needs REAL.
2Constant or variable? + DECLARE (4 marks) — Getting started
Getting started• variables, constants, declare
Question
A program works out the cost of tickets. Each ticket is a fixed 8 dollars; the number of tickets varies each run. (a) State whether the ticket price should be a constant or a variable, and why. (2) (b) Write 0478 pseudocode that DECLAREs an INTEGER variable NumTickets and a constant for the price, then assigns the price. (2)
Step-by-step solution
1. Step 1
  (a) Constant (2 marks). The ticket price never changes while the program runs, so it should be a CONSTANT. A constant documents that the value is fixed and stops it being changed by accident. NumTickets changes each run, so it is a variable.
2. Step 2
  (b) Declaration (1 mark) + constant (1 mark). In 0478 pseudocode, variables are introduced with DECLARE <name> : <TYPE> and constants with CONSTANT <name> ← <value>.
Answer
DECLARE NumTickets : INTEGER CONSTANT Price = 8

The price is a CONSTANT (fixed); NumTickets is a variable (changes each run).
Examiner tip
AO2. Mark scheme: 1 for the correct DECLARE…:INTEGER line, 1 for using CONSTANT for the fixed price. Writing Price ← 8 as a plain variable loses the constant mark.
3Build a condition with logical operators (4 marks) — Building confidence
Building confidence• operators, selection
Question
A theme-park ride is open to a person only if they are at least 12 years old AND at most 70 years old. Write an IF statement in 0478 pseudocode that OUTPUTs "Allowed" when both conditions hold and "Refused" otherwise. Age is stored in INTEGER variable Age.
Step-by-step solution
1. Step 1
  Relational operators (1 mark). 'At least 12' is Age >= 12; 'at most 70' is Age <= 70. The 0478 relational operators are = <> < > <= >=.
2. Step 2
  Logical operator (1 mark). Both conditions must be true together, so join them with AND. (OR would wrongly allow anyone over 70 or under 12.)
3. Step 3
  IF…ELSE…ENDIF structure (2 marks). Selection uses IF condition THEN … ELSE … ENDIF.
Answer
IF Age >= 12 AND Age <= 70 THEN OUTPUT "Allowed" ELSE OUTPUT "Refused" ENDIF
Examiner tip
AO2. 1 mark each: correct lower bound, correct upper bound, AND, correct IF/ELSE/ENDIF. A frequent error is using > instead of >=, which wrongly refuses a 12-year-old.
4Totalling & counting with a WHILE loop (6 marks) — Building confidence
Building confidence• iteration, while, totalling, counting
Question
Numbers are entered one at a time until the user enters -1 (the sentinel). The -1 must NOT be counted or added. Using a pre-condition WHILE loop, output how many real numbers were entered and their total.
Step-by-step solution
1. Step 1
  Initialise the running total and count (1 mark). Before the loop, set Total ← 0 and Count ← 0. Forgetting to initialise is the single most common totalling error.
2. Step 2
  Read the FIRST value before the loop (1 mark). A pre-condition WHILE tests its condition first, so we must have a value to test. This is the 'priming read'.
3. Step 3
  Loop while not the sentinel (1 mark). WHILE Num <> -1 — the body only runs for genuine data, so -1 is never counted.
4. Step 4
  Update total and count, then read again (2 marks). Inside the loop, add Num to Total and add 1 to Count, then INPUT the next Num so the loop can end.
5. Step 5
  Output after the loop (1 mark). Once -1 is read, the loop ends and we OUTPUT Count and Total.
Answer
Total ← 0 Count ← 0 OUTPUT "Enter a number (-1 to stop):" INPUT Num WHILE Num <> -1 Total ← Total + Num Count ← Count + 1 OUTPUT "Enter a number (-1 to stop):" INPUT Num ENDWHILE OUTPUT "You entered ", Count, " numbers" OUTPUT "Total = ", Total
Examiner tip
AO3. Marks: initialise Total & Count, priming INPUT, correct WHILE condition with sentinel, total/count updates, re-INPUT inside loop, correct OUTPUT. Omitting the re-INPUT gives an infinite loop and loses 2 marks.
5Build initials with string handling (6 marks) — Stretch
Stretch• strings, substring, length, ucase
Question
FirstName and LastName are STRING variables (each at least one character). Using 0478 string functions, build a STRING Initials containing the first letter of each name in UPPER CASE, separated by a dot — e.g. "jane" and "smith" → "J.S". Then output it. Functions available: LENGTH(s), SUBSTRING(s, start, length) (1-based start), UCASE(s).
Step-by-step solution
1. Step 1
  Extract the first character (2 marks). SUBSTRING(FirstName, 1, 1) takes 1 character starting at position 1. 0478 SUBSTRING is 1-based, so position 1 is the first letter.
2. Step 2
  Force upper case (1 mark). Wrap each extracted character in UCASE so "jane" gives 'J' regardless of how it was typed.
3. Step 3
  Concatenate with the dot (2 marks). Join the two upper-case initials with "&" (string concatenation in 0478) putting "." between them.
4. Step 4
  Output (1 mark). OUTPUT the assembled Initials string.
Answer
FirstInitial ← UCASE(SUBSTRING(FirstName, 1, 1)) LastInitial ← UCASE(SUBSTRING(LastName, 1, 1)) Initials ← FirstInitial & "." & LastInitial OUTPUT Initials
Examiner tip
AO3. Marks: correct SUBSTRING(…,1,1) on each name (×2), UCASE applied, concatenation with the dot in the right order, OUTPUT. A common slip is treating SUBSTRING as 0-based and starting at position 0.
6Nested selection inside a validation loop (6 marks) — Stretch
Stretch• iteration, repeat, nested, validation
Question
A login PIN must be a 4-digit INTEGER between 1000 and 9999. Using a post-condition REPEAT…UNTIL loop, keep asking for a PIN until a valid one is entered. Inside the loop, OUTPUT a specific message saying whether the rejected PIN was too small or too large. Then confirm acceptance.
Step-by-step solution
1. Step 1
  Choose REPEAT…UNTIL (1 mark). We must ask at least once, so a post-condition loop (which runs the body before testing) is the natural fit. The loop ends UNTIL the PIN is in range.
2. Step 2
  INPUT inside the loop (1 mark). Each pass reads a fresh Pin so the user can correct a mistake.
3. Step 3
  Nested IF for the feedback (2 marks). Inside the loop, an IF…ELSE IF gives a different message for too small (< 1000) versus too large (> 9999). This nested selection lives inside the iteration.
4. Step 4
  Correct exit condition (1 mark). UNTIL Pin >= 1000 AND Pin <= 9999 — the loop only stops when the PIN is in the valid range.
5. Step 5
  Confirm after the loop (1 mark). Once the loop ends the PIN is guaranteed valid, so OUTPUT an acceptance message.
Answer
REPEAT OUTPUT "Enter a 4-digit PIN (1000-9999):" INPUT Pin IF Pin < 1000 THEN OUTPUT "PIN too small - try again" ELSE IF Pin > 9999 THEN OUTPUT "PIN too large - try again" ENDIF ENDIF UNTIL Pin >= 1000 AND Pin <= 9999 OUTPUT "PIN accepted"
Examiner tip
AO3. Marks: REPEAT…UNTIL chosen, INPUT inside loop, nested IF distinguishing too-small vs too-large, correct AND exit condition, acceptance output. Note the body always runs once — exactly why a post-condition loop suits 'ask at least once' validation.

Model Answers — Programming Concepts

High-scoring sample answers for programming concepts on the Cambridge IGCSE 0478 paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.

Question 1
0478 Paper 2 — style2 marks
A program stores the maximum number of players in a team, which is fixed at 11. Write 2 marks of 0478 pseudocode that declares this as a constant and a separate INTEGER variable PlayerCount initialised to 0.
Model answer
CONSTANT MaxPlayers = 11 DECLARE PlayerCount : INTEGER PlayerCount ← 0
Why this scores
AO2. 1 mark: CONSTANT used for the fixed value 11. 1 mark: PlayerCount declared as INTEGER and set to 0. Using a plain variable for the fixed 11 (e.g. MaxPlayers ← 11) loses the constant mark.
Question 2
0478 Paper 2 — style4 marks
Write a count-controlled loop in 0478 pseudocode that outputs the 7 times table from 7 × 1 up to 7 × 12, one line per result. 4 marks
Model answer
FOR Multiplier ← 1 TO 12 Result ← 7 * Multiplier OUTPUT "7 x ", Multiplier, " = ", Result NEXT Multiplier
Why this scores
AO3. 1 mark: FOR…TO with correct bounds 1 to 12. 1 mark: NEXT closing the loop. 1 mark: correct multiplication 7 * Multiplier. 1 mark: OUTPUT showing the result. A FOR loop is correct here because the number of iterations (12) is known in advance.
Question 3
0478 Paper 2 — style6 marks
Twenty INTEGER scores are entered. Using a count-controlled loop and selection, output the largest score entered. 6 marks
Model answer
DECLARE Score : INTEGER DECLARE Largest : INTEGER OUTPUT "Enter score 1:" INPUT Score Largest ← Score FOR Counter ← 2 TO 20 OUTPUT "Enter next score:" INPUT Score IF Score > Largest THEN Largest ← Score ENDIF NEXT Counter OUTPUT "Largest score = ", Largest
Why this scores
AO3. 1 mark: read first score and set it as the initial Largest. 1 mark: FOR loop covering the remaining 19 scores. 1 mark: INPUT inside the loop. 2 marks: IF Score > Largest THEN update Largest. 1 mark: OUTPUT Largest after the loop. Seeding Largest with the first input (rather than 0) is what makes negative-only data work correctly.
Question 4
0478 Paper 2 — style8 marks
A teacher enters 10 test marks, each of which must be between 0 and 100 inclusive. Reject and re-ask for any out-of-range mark. After all 10 valid marks are entered, output the average as a REAL. 8 marks
Model answer
DECLARE Mark : INTEGER DECLARE Total : INTEGER DECLARE Average : REAL Total ← 0 FOR Counter ← 1 TO 10 REPEAT OUTPUT "Enter mark ", Counter, " (0-100):" INPUT Mark IF Mark < 0 OR Mark > 100 THEN OUTPUT "Invalid - mark must be 0 to 100" ENDIF UNTIL Mark >= 0 AND Mark <= 100 Total ← Total + Mark NEXT Counter Average ← Total / 10 OUTPUT "Average = ", Average
Why this scores
AO3. 1: initialise Total ← 0. 1: FOR loop for the 10 marks. 1: REPEAT…UNTIL validation loop. 2: range check (< 0 OR > 100) with re-prompt. 1: correct UNTIL exit condition. 1: add valid Mark to Total. 1: compute and OUTPUT Average as Total / 10. The REPEAT nests inside the FOR — outer loop counts the 10 marks, inner loop guarantees each is valid.
Question 5
0478 Paper 2 — style12 marks
A STRING Sentence is entered. Using string-handling functions, count how many of its characters are vowels (a, e, i, o, u — upper or lower case) and output the count. 12 marks Available: LENGTH(s), SUBSTRING(s, start, length) (1-based), UCASE(s).
Model answer
DECLARE Sentence : STRING DECLARE Ch : CHAR DECLARE VowelCount : INTEGER DECLARE Position : INTEGER VowelCount ← 0 OUTPUT "Enter a sentence:" INPUT Sentence FOR Position ← 1 TO LENGTH(Sentence) Ch ← UCASE(SUBSTRING(Sentence, Position, 1)) IF Ch = 'A' OR Ch = 'E' OR Ch = 'I' OR Ch = 'O' OR Ch = 'U' THEN VowelCount ← VowelCount + 1 ENDIF NEXT Position OUTPUT "Number of vowels = ", VowelCount
Why this scores
AO3 (12 marks). 1: declare/initialise VowelCount ← 0. 1: INPUT Sentence. 2: FOR loop bounded by LENGTH(Sentence). 2: SUBSTRING(Sentence, Position, 1) to read each character. 1: UCASE to make the test case-insensitive. 3: IF testing the character against all five vowels with OR. 1: increment VowelCount on a match. 1: OUTPUT the count after the loop. Looping to LENGTH(Sentence) with a 1-based SUBSTRING covers every character exactly once — off-by-one slips (starting at 0, or to LENGTH-1) are the usual lost marks.
Question 6
0478 Paper 2 — style15 marks
15-mark unseen scenario. A cinema sells tickets for a single film showing that has 100 seats.
- The program repeatedly processes customers until the operator enters the word "CLOSED" instead of a customer name.
- For each customer it reads the number of tickets they want (1 to 6).
- A ticket costs 9 dollars, but customers buying 4 or more tickets get a 10% discount on their whole order.
- A booking must be refused if there are not enough seats left.
- At the end, output: the total number of tickets sold, the total money taken, and the number of seats remaining.
Write an algorithm in 0478 pseudocode using suitable variables, constants, loops and selection. 15 marks
Model answer
CONSTANT TotalSeats = 100 CONSTANT TicketPrice = 9 DECLARE Name : STRING DECLARE NumTickets : INTEGER DECLARE SeatsLeft : INTEGER DECLARE TicketsSold : INTEGER DECLARE MoneyTaken : REAL DECLARE Cost : REAL SeatsLeft ← TotalSeats TicketsSold ← 0 MoneyTaken ← 0 OUTPUT "Enter customer name (or CLOSED to finish):" INPUT Name WHILE Name <> "CLOSED" REPEAT OUTPUT "How many tickets (1-6)?" INPUT NumTickets UNTIL NumTickets >= 1 AND NumTickets <= 6 IF NumTickets > SeatsLeft THEN OUTPUT "Sorry - not enough seats left. Booking refused." ELSE Cost ← NumTickets * TicketPrice IF NumTickets >= 4 THEN Cost ← Cost * 0.9 ENDIF SeatsLeft ← SeatsLeft - NumTickets TicketsSold ← TicketsSold + NumTickets MoneyTaken ← MoneyTaken + Cost OUTPUT "Booking confirmed. Cost = ", Cost ENDIF OUTPUT "Enter customer name (or CLOSED to finish):" INPUT Name ENDWHILE OUTPUT "Tickets sold = ", TicketsSold OUTPUT "Money taken = ", MoneyTaken OUTPUT "Seats remaining = ", SeatsLeft
Why this scores
AO3 (15 marks), mapped: (1) CONSTANT for the 100 seats; (1) CONSTANT for the 9-dollar price; (1) initialise SeatsLeft, TicketsSold, MoneyTaken; (1) priming INPUT Name before the WHILE; (2) WHILE Name <> "CLOSED" with re-INPUT inside the loop so the sentinel ends it; (2) REPEAT…UNTIL validating tickets are 1–6; (2) IF NumTickets > SeatsLeft refuses the booking, ELSE processes it; (1) Cost ← NumTickets * TicketPrice; (2) IF NumTickets >= 4 THEN apply 10% discount (Cost * 0.9); (1) update SeatsLeft, TicketsSold and MoneyTaken on a confirmed booking; (2) final OUTPUT of tickets sold, money taken and seats remaining. Marks are gained by correctly combining constants, a sentinel-controlled WHILE, nested validation REPEAT and nested selection — exactly the synthesis the final Paper 2 question rewards. The refusal check must come BEFORE seats are deducted, or an over-booking silently goes through.

Key Definitions and Keywords — Programming Concepts

Definitions to memorise and the exact keywords mark schemes credit for programming concepts answers — sharpened from recent examiner reports for the 2026 0478 sitting.

Variable
Examiner keyword
A named storage location whose value CAN CHANGE while the program runs.
Constant
Examiner keyword
A named storage location whose value DOES NOT CHANGE after it's set. Used for values like π, conversion factors, configuration limits.
Integer
Examiner keyword
Whole-number data type — no decimal places. Examples: -3, 0, 42.
Real (Float)
Examiner keyword
Numeric data type WITH decimal places. Examples: 3.14, -0.5, 2.0.
Boolean
Examiner keyword
Data type with only two values: TRUE or FALSE.
String
Examiner keyword
A sequence of characters of arbitrary length. Used for text.
Char
Examiner keyword
A single character. Often a separate type from String in strongly-typed languages.
Procedure
Examiner keyword
A subroutine that performs a task but does NOT return a value.
Function
Examiner keyword
A subroutine that performs a task AND returns a value.
Parameter
Examiner keyword
A variable that receives the value of an ARGUMENT passed to a subroutine. Lets the same subroutine work on different inputs.
Local variable
Examiner keyword
A variable declared inside a subroutine; accessible only within that subroutine.
Global variable
Examiner keyword
A variable declared outside any subroutine; accessible everywhere in the program.
String LENGTH function
Returns the number of characters in a string. Cambridge pseudocode: LENGTH(text).
String SUBSTRING function
Returns a portion of a string given start position and length. Cambridge pseudocode: SUBSTRING(text, start, length).

Common Mistakes and Misconceptions — Programming Concepts

The traps other students keep falling into on programming concepts questions — taken from recent Cambridge IGCSE 0478 examiner reports and mark schemes — and how to avoid them.

✕Using a variable for something that should be a constant
0478 Examiner Reports 2022-2024
Why it happens
Students declare everything as a variable.
How to avoid it
If the value WON'T change (π, VAT rate at the time of the program, max users), use a CONSTANT. Documents intent and prevents accidental modification.
✕Using Integer for prices
Why it happens
Prices look like 'whole numbers'.
How to avoid it
Prices have pence/cents — use REAL (or a dedicated Currency/Decimal type). Integer prices lose accuracy on calculations.
✕Calling a procedure a function (or vice versa)
Why it happens
Both are 'subroutines'.
How to avoid it
Function RETURNS a value. Procedure does NOT return a value. The distinction is exactly that one rule.
✕Making every variable global
Why it happens
Globals are accessible everywhere; feels easier.
How to avoid it
Overuse of globals leads to spaghetti code and bugs from unintended side effects. Default to LOCAL; promote to global only when truly needed.

Programming Concepts — frequently asked questions

The things students keep getting wrong in this sub-topic, answered.

Type

Stores

Example

Integer

Whole numbers

-3, 0, 42

Real (Float)

Numbers with decimals

3.14, -0.5

Boolean

TRUE / FALSE

TRUE

String

Sequence of characters

"Hello"

Char

Single character

'A'

Date

Date / DateTime

09/05/2026

Strings are sequences of characters; Cambridge has a small set of built-in functions for manipulating them.

LENGTH(text). Returns the number of characters.

LENGTH("Hello")  → 5

SUBSTRING(text, start, length). Returns a slice of the string.

SUBSTRING("Computer", 1, 4)  → "Comp"
SUBSTRING("Computer", 5, 4)  → "uter"

UCASE(text). Convert to uppercase.

UCASE("hello")  → "HELLO"

LCASE(text). Convert to lowercase.

LCASE("WORLD")  → "world"

Concatenation (+). Join strings together.

Greeting ← "Hello, " + Name

Cambridge tip. Use Cambridge pseudocode names (LENGTH, SUBSTRING, UCASE, LCASE) — not Python's len/slice or Java's .length(). Mark schemes deduct for language-specific syntax.

Total ← 0 Count ← 0 OUTPUT "Enter a number (-1 to stop):" INPUT Num WHILE Num <> -1 Total ← Total + Num Count ← Count + 1 OUTPUT "Enter a number (-1 to stop):" INPUT Num ENDWHILE OUTPUT "You entered ", Count, " numbers" OUTPUT "Total = ", Total

REPEAT OUTPUT "Enter a 4-digit PIN (1000-9999):" INPUT Pin IF Pin < 1000 THEN OUTPUT "PIN too small - try again" ELSE IF Pin > 9999 THEN OUTPUT "PIN too large - try again" ENDIF ENDIF UNTIL Pin >= 1000 AND Pin <= 9999 OUTPUT "PIN accepted"

DECLARE Score : INTEGER DECLARE Largest : INTEGER OUTPUT "Enter score 1:" INPUT Score Largest ← Score FOR Counter ← 2 TO 20 OUTPUT "Enter next score:" INPUT Score IF Score > Largest THEN Largest ← Score ENDIF NEXT Counter OUTPUT "Largest score = ", Largest

DECLARE Mark : INTEGER DECLARE Total : INTEGER DECLARE Average : REAL Total ← 0 FOR Counter ← 1 TO 10 REPEAT OUTPUT "Enter mark ", Counter, " (0-100):" INPUT Mark IF Mark < 0 OR Mark > 100 THEN OUTPUT "Invalid - mark must be 0 to 100" ENDIF UNTIL Mark >= 0 AND Mark <= 100 Total ← Total + Mark NEXT Counter Average ← Total / 10 OUTPUT "Average = ", Average

DECLARE Sentence : STRING DECLARE Ch : CHAR DECLARE VowelCount : INTEGER DECLARE Position : INTEGER VowelCount ← 0 OUTPUT "Enter a sentence:" INPUT Sentence FOR Position ← 1 TO LENGTH(Sentence) Ch ← UCASE(SUBSTRING(Sentence, Position, 1)) IF Ch = 'A' OR Ch = 'E' OR Ch = 'I' OR Ch = 'O' OR Ch = 'U' THEN VowelCount ← VowelCount + 1 ENDIF NEXT Position OUTPUT "Number of vowels = ", VowelCount

CONSTANT TotalSeats = 100 CONSTANT TicketPrice = 9 DECLARE Name : STRING DECLARE NumTickets : INTEGER DECLARE SeatsLeft : INTEGER DECLARE TicketsSold : INTEGER DECLARE MoneyTaken : REAL DECLARE Cost : REAL SeatsLeft ← TotalSeats TicketsSold ← 0 MoneyTaken ← 0 OUTPUT "Enter customer name (or CLOSED to finish):" INPUT Name WHILE Name <> "CLOSED" REPEAT OUTPUT "How many tickets (1-6)?" INPUT NumTickets UNTIL NumTickets >= 1 AND NumTickets <= 6 IF NumTickets > SeatsLeft THEN OUTPUT "Sorry - not enough seats left. Booking refused." ELSE Cost ← NumTickets * TicketPrice IF NumTickets >= 4 THEN Cost ← Cost * 0.9 ENDIF SeatsLeft ← SeatsLeft - NumTickets TicketsSold ← TicketsSold + NumTickets MoneyTaken ← MoneyTaken + Cost OUTPUT "Booking confirmed. Cost = ", Cost ENDIF OUTPUT "Enter customer name (or CLOSED to finish):" INPUT Name ENDWHILE OUTPUT "Tickets sold = ", TicketsSold OUTPUT "Money taken = ", MoneyTaken OUTPUT "Seats remaining = ", SeatsLeft

Programming Concepts

Short Notes - Programming Concepts

Detailed Study Notes

At a glance

What you’ll learn

Variables and constants

Common data types

Procedures and functions

Local vs global scope

String-manipulation functions

Quick recap

Memorise this

How it’s examined

Take this whole topic with you

1Choose the correct data type (5 marks) — Getting started

2Constant or variable? + DECLARE (4 marks) — Getting started

3Build a condition with logical operators (4 marks) — Building confidence

4Totalling & counting with a WHILE loop (6 marks) — Building confidence

5Build initials with string handling (6 marks) — Stretch

6Nested selection inside a validation loop (6 marks) — Stretch

Variable

Constant

Integer

Real (Float)

Boolean

String

Char

Procedure

Function

Parameter

Local variable

Global variable

String LENGTH function

String SUBSTRING function

✕Using a variable for something that should be a constant

✕Using Integer for prices

✕Calling a procedure a function (or vice versa)

✕Making every variable global

Programming Concepts — frequently asked questions

Programming Concepts

Short Notes - Programming Concepts

Detailed Study Notes

At a glance

What you’ll learn

Variables and constants

Common data types

Procedures and functions

Local vs global scope

String-manipulation functions

Quick recap

Memorise this

How it’s examined

Take this whole topic with you

1Choose the correct data type (5 marks) — Getting started

2Constant or variable? + DECLARE (4 marks) — Getting started

3Build a condition with logical operators (4 marks) — Building confidence

4Totalling & counting with a WHILE loop (6 marks) — Building confidence

5Build initials with string handling (6 marks) — Stretch

6Nested selection inside a validation loop (6 marks) — Stretch

Variable

Constant

Integer

Real (Float)

Boolean

String

Char

Procedure

Function

Parameter

Local variable

Global variable

String LENGTH function

String SUBSTRING function

✕Using a variable for something that should be a constant