Learn Modula3 - 10 Code Examples & CST Typing Practice Test

Modula-3 is a high-level, statically typed programming language designed for safe systems programming, modularity, and object-oriented programming. It emphasizes simplicity, safety, and readability while providing features suitable for building large, robust software systems.

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Modula-3 Counter and Theme Toggle Modula-3 Random Number Generator Modula-3 Todo List Modula-3 Dice Roller Modula-3 Countdown Timer Modula-3 Prime Checker Modula-3 Temperature Converter Modula-3 Shopping Cart Modula-3 Name Greeting Modula-3 Stopwatch

Learn MODULA3 with Real Code Examples

Updated Nov 21, 2025

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Code Sample Descriptions

Modula-3 Counter and Theme Toggle

MODULE CounterTheme;

IMPORT IO;

VAR
    count: INTEGER := 0;
    isDark: BOOLEAN := FALSE;

PROCEDURE updateUI():=BEGIN
    IO.Put("Counter: "); IO.PutInt(count, 0); IO.PutLn();
    IF isDark THEN
        IO.PutLn("Theme: Dark")
    ELSE
        IO.PutLn("Theme: Light")
    END;
END updateUI;

PROCEDURE increment():=BEGIN
    count := count + 1;
    updateUI();
END increment;

PROCEDURE decrement():=BEGIN
    count := count - 1;
    updateUI();
END decrement;

PROCEDURE reset():=BEGIN
    count := 0;
    updateUI();
END reset;

PROCEDURE toggleTheme():=BEGIN
    isDark := NOT isDark;
    updateUI();
END toggleTheme;

BEGIN
    updateUI();
    increment();
    increment();
    toggleTheme();
    decrement();
    reset();
END CounterTheme.

Demonstrates a simple counter with theme toggling using Modula-3 variables, procedures, and safe I/O.

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Modula-3 Random Number Generator

MODULE RandomGen;
IMPORT IO, SYSTEM;
VAR i, num: INTEGER;
BEGIN
    FOR i := 1 TO 3 DO
        num := SYSTEM.Random() MOD 100 + 1;
        IO.Put("Random "); IO.PutInt(i,0); IO.Put(" : "); IO.PutInt(num,0); IO.PutLn();
    END;
END RandomGen.

Generates random numbers between 1 and 100 and prints them.

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Modula-3 Todo List

MODULE TodoList;
IMPORT IO;
VAR todos: ARRAY [0..9] OF STRING;
VAR count: INTEGER := 0;

PROCEDURE addTask(task: STRING);
BEGIN
    todos[count] := task; count := count + 1;
    FOR i := 0 TO count-1 DO IO.PutLn(todos[i]) END;
END addTask;

PROCEDURE removeTask(index: INTEGER);
VAR i: INTEGER;
BEGIN
    FOR i := index TO count-2 DO todos[i] := todos[i+1] END;
    count := count - 1;
    FOR i := 0 TO count-1 DO IO.PutLn(todos[i]) END;
END removeTask;

BEGIN
    addTask("Buy milk");
    addTask("Write Modula-3 code");
    removeTask(0);
END TodoList.

Maintains a simple todo list with add and remove functionality.

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Modula-3 Dice Roller

MODULE DiceRoll;
IMPORT IO, SYSTEM;
VAR i, roll: INTEGER;
BEGIN
    FOR i := 1 TO 3 DO
        roll := SYSTEM.Random() MOD 6 + 1;
        IO.Put("Roll "); IO.PutInt(i,0); IO.Put(" : "); IO.PutInt(roll,0); IO.PutLn();
    END;
END DiceRoll.

Rolls a six-sided dice three times.

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Modula-3 Countdown Timer

MODULE Countdown;
IMPORT IO;
VAR count: INTEGER := 5;
BEGIN
    WHILE count >= 0 DO
        IO.Put("Countdown: "); IO.PutInt(count,0); IO.PutLn();
        count := count - 1;
    END;
    IO.PutLn("Done!");
END Countdown.

Counts down from 5 to 0.

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Modula-3 Prime Checker

MODULE PrimeCheck;
IMPORT IO;
VAR nums: ARRAY [0..2] OF INTEGER := [7,10,13];
VAR n, i: INTEGER;
VAR isPrime: BOOLEAN;
BEGIN
    FOR n IN nums DO
        isPrime := TRUE;
        FOR i := 2 TO n-1 DO
        IF n MOD i = 0 THEN isPrime := FALSE END;
        END;
        IO.PutInt(n,0);
        IF isPrime THEN IO.PutLn(" is Prime") ELSE IO.PutLn(" is Not Prime") END;
    END;
END PrimeCheck.

Checks if numbers are prime.

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Modula-3 Temperature Converter

MODULE TempConv;
IMPORT IO;

PROCEDURE cToF(c: REAL): REAL;
BEGIN RETURN c*9/5+32 END cToF;

PROCEDURE fToC(f: REAL): REAL;
BEGIN RETURN (f-32)*5/9 END fToC;

BEGIN
    IO.Put("25°C = "); IO.PutReal(cToF(25),2); IO.PutLn();
    IO.Put("77°F = "); IO.PutReal(fToC(77),2); IO.PutLn();
END TempConv.

Converts Celsius to Fahrenheit and Fahrenheit to Celsius.

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Modula-3 Shopping Cart

MODULE ShoppingCart;
IMPORT IO;
VAR cart: ARRAY [0..9] OF STRING;
VAR prices: ARRAY [0..9] OF INTEGER;
VAR count: INTEGER := 0;

PROCEDURE addItem(item: STRING; price: INTEGER);
BEGIN
    cart[count] := item; prices[count] := price; count := count + 1;
    (* print cart and total sum here *)
END addItem;

PROCEDURE removeItem(index: INTEGER);
VAR i: INTEGER;
BEGIN
    FOR i := index TO count-2 DO cart[i] := cart[i+1]; prices[i] := prices[i+1] END;
    count := count -1;
    (* print cart and total sum here *)
END removeItem;

BEGIN
    addItem("Apple", 2);
    addItem("Banana", 3);
    removeItem(0);
END ShoppingCart.

Adds and removes items in a shopping cart with total cost.

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Modula-3 Name Greeting

MODULE Greet;
IMPORT IO;
PROCEDURE greet(name: STRING);
BEGIN
    IO.Put("Hello, "); IO.Put(name); IO.PutLn("! Welcome!");
END greet;

BEGIN
    greet("Saurav");
    greet("Alice");
    greet("Bob");
END Greet.

Greets users by name.

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Modula-3 Stopwatch

MODULE Stopwatch;
IMPORT IO;
VAR time: INTEGER := 0;
BEGIN
    WHILE time < 5 DO
        IO.Put("Stopwatch: "); IO.PutInt(time,0); IO.PutLn();
        time := time + 1;
    END;
    IO.PutLn("Done!");
END Stopwatch.

Simulates a stopwatch incrementing seconds.

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Frequently Asked Questions about Modula3

What is Modula3?

What are the primary use cases for Modula3?

Safe systems programming. Concurrent applications. Compiler development. Networked and distributed systems. Educational projects on modular programming

What are the strengths of Modula3?

High-level abstraction with system-level control. Safe and reliable code through static typing and garbage collection. Supports modular and object-oriented design. Concurrency built into the language. Readable and maintainable syntax

What are the limitations of Modula3?

Smaller community compared to mainstream languages. Limited library ecosystem and tooling. Primarily academic or research use. Not widely used in modern commercial software. Performance can be impacted by garbage collection

How can I practice Modula3 typing speed?

CodeSpeedTest offers 10+ real Modula3 code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Modula-3 Counter and Theme Toggle

MODULE CounterTheme;

IMPORT IO;

VAR
    count: INTEGER := 0;
    isDark: BOOLEAN := FALSE;

PROCEDURE updateUI():=BEGIN
    IO.Put("Counter: "); IO.PutInt(count, 0); IO.PutLn();
    IF isDark THEN
        IO.PutLn("Theme: Dark")
    ELSE
        IO.PutLn("Theme: Light")
    END;
END updateUI;

PROCEDURE increment():=BEGIN
    count := count + 1;
    updateUI();
END increment;

PROCEDURE decrement():=BEGIN
    count := count - 1;
    updateUI();
END decrement;

PROCEDURE reset():=BEGIN
    count := 0;
    updateUI();
END reset;

PROCEDURE toggleTheme():=BEGIN
    isDark := NOT isDark;
    updateUI();
END toggleTheme;

BEGIN
    updateUI();
    increment();
    increment();
    toggleTheme();
    decrement();
    reset();
END CounterTheme.

Demonstrates a simple counter with theme toggling using Modula-3 variables, procedures, and safe I/O.

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Modula-3 Random Number Generator

MODULE RandomGen;
IMPORT IO, SYSTEM;
VAR i, num: INTEGER;
BEGIN
    FOR i := 1 TO 3 DO
        num := SYSTEM.Random() MOD 100 + 1;
        IO.Put("Random "); IO.PutInt(i,0); IO.Put(" : "); IO.PutInt(num,0); IO.PutLn();
    END;
END RandomGen.

Generates random numbers between 1 and 100 and prints them.

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Modula-3 Todo List

MODULE TodoList;
IMPORT IO;
VAR todos: ARRAY [0..9] OF STRING;
VAR count: INTEGER := 0;

PROCEDURE addTask(task: STRING);
BEGIN
    todos[count] := task; count := count + 1;
    FOR i := 0 TO count-1 DO IO.PutLn(todos[i]) END;
END addTask;

PROCEDURE removeTask(index: INTEGER);
VAR i: INTEGER;
BEGIN
    FOR i := index TO count-2 DO todos[i] := todos[i+1] END;
    count := count - 1;
    FOR i := 0 TO count-1 DO IO.PutLn(todos[i]) END;
END removeTask;

BEGIN
    addTask("Buy milk");
    addTask("Write Modula-3 code");
    removeTask(0);
END TodoList.

Maintains a simple todo list with add and remove functionality.

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Modula-3 Dice Roller

MODULE DiceRoll;
IMPORT IO, SYSTEM;
VAR i, roll: INTEGER;
BEGIN
    FOR i := 1 TO 3 DO
        roll := SYSTEM.Random() MOD 6 + 1;
        IO.Put("Roll "); IO.PutInt(i,0); IO.Put(" : "); IO.PutInt(roll,0); IO.PutLn();
    END;
END DiceRoll.

Rolls a six-sided dice three times.

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Modula-3 Countdown Timer

MODULE Countdown;
IMPORT IO;
VAR count: INTEGER := 5;
BEGIN
    WHILE count >= 0 DO
        IO.Put("Countdown: "); IO.PutInt(count,0); IO.PutLn();
        count := count - 1;
    END;
    IO.PutLn("Done!");
END Countdown.

Counts down from 5 to 0.

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Modula-3 Prime Checker

MODULE PrimeCheck;
IMPORT IO;
VAR nums: ARRAY [0..2] OF INTEGER := [7,10,13];
VAR n, i: INTEGER;
VAR isPrime: BOOLEAN;
BEGIN
    FOR n IN nums DO
        isPrime := TRUE;
        FOR i := 2 TO n-1 DO
        IF n MOD i = 0 THEN isPrime := FALSE END;
        END;
        IO.PutInt(n,0);
        IF isPrime THEN IO.PutLn(" is Prime") ELSE IO.PutLn(" is Not Prime") END;
    END;
END PrimeCheck.

Checks if numbers are prime.

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Modula-3 Temperature Converter

MODULE TempConv;
IMPORT IO;

PROCEDURE cToF(c: REAL): REAL;
BEGIN RETURN c*9/5+32 END cToF;

PROCEDURE fToC(f: REAL): REAL;
BEGIN RETURN (f-32)*5/9 END fToC;

BEGIN
    IO.Put("25°C = "); IO.PutReal(cToF(25),2); IO.PutLn();
    IO.Put("77°F = "); IO.PutReal(fToC(77),2); IO.PutLn();
END TempConv.

Converts Celsius to Fahrenheit and Fahrenheit to Celsius.

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Modula-3 Shopping Cart

MODULE ShoppingCart;
IMPORT IO;
VAR cart: ARRAY [0..9] OF STRING;
VAR prices: ARRAY [0..9] OF INTEGER;
VAR count: INTEGER := 0;

PROCEDURE addItem(item: STRING; price: INTEGER);
BEGIN
    cart[count] := item; prices[count] := price; count := count + 1;
    (* print cart and total sum here *)
END addItem;

PROCEDURE removeItem(index: INTEGER);
VAR i: INTEGER;
BEGIN
    FOR i := index TO count-2 DO cart[i] := cart[i+1]; prices[i] := prices[i+1] END;
    count := count -1;
    (* print cart and total sum here *)
END removeItem;

BEGIN
    addItem("Apple", 2);
    addItem("Banana", 3);
    removeItem(0);
END ShoppingCart.

Adds and removes items in a shopping cart with total cost.

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Modula-3 Name Greeting

MODULE Greet;
IMPORT IO;
PROCEDURE greet(name: STRING);
BEGIN
    IO.Put("Hello, "); IO.Put(name); IO.PutLn("! Welcome!");
END greet;

BEGIN
    greet("Saurav");
    greet("Alice");
    greet("Bob");
END Greet.

Greets users by name.

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Modula-3 Stopwatch

MODULE Stopwatch;
IMPORT IO;
VAR time: INTEGER := 0;
BEGIN
    WHILE time < 5 DO
        IO.Put("Stopwatch: "); IO.PutInt(time,0); IO.PutLn();
        time := time + 1;
    END;
    IO.PutLn("Done!");
END Stopwatch.

Simulates a stopwatch incrementing seconds.

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Frequently Asked Questions about Modula3

What is Modula3?

What are the primary use cases for Modula3?

Safe systems programming. Concurrent applications. Compiler development. Networked and distributed systems. Educational projects on modular programming

What are the strengths of Modula3?

What are the limitations of Modula3?

How can I practice Modula3 typing speed?

CodeSpeedTest offers 10+ real Modula3 code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.