Learn MODULA2 with Real Code Examples

MODULE CounterTheme;

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

PROCEDURE updateUI;
BEGIN
    WriteString("Counter: "); WriteInt(count, 0); WriteLn;
    IF isDark THEN
        WriteString("Theme: Dark"); WriteLn
    ELSE
        WriteString("Theme: Light"); WriteLn;
    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-2 variables and procedures.

MODULE RandomGen;
IMPORT InOut;
VAR i, num: INTEGER;
BEGIN
    FOR i := 1 TO 3 DO
        num := RANDOM(100) + 1;
        InOut.WriteString("Random "); InOut.WriteInt(i,0); InOut.WriteString(": "); InOut.WriteInt(num,0); InOut.WriteLn;
    END;
END RandomGen.

Generates random numbers between 1 and 100 and prints them.

MODULE TodoList;
IMPORT InOut;
VAR todos: ARRAY 10 OF ARRAY 50 OF CHAR; count: INTEGER := 0;

PROCEDURE addTask(task: ARRAY OF CHAR);
BEGIN
    todos[count] := task; count := count + 1;
    FOR i := 0 TO count-1 DO InOut.WriteString(todos[i]); InOut.WriteLn END;
END addTask;

PROCEDURE removeTask(idx: INTEGER);
VAR i: INTEGER;
BEGIN
    FOR i := idx TO count-2 DO todos[i] := todos[i+1] END;
    count := count - 1;
    FOR i := 0 TO count-1 DO InOut.WriteString(todos[i]); InOut.WriteLn END;
END removeTask;

BEGIN
    addTask("Buy milk");
    addTask("Write Modula-2 code");
    removeTask(0);
END TodoList.

Maintains a simple todo list with add and remove functionality.

MODULE DiceRoll;
IMPORT InOut;
VAR i, roll: INTEGER;
BEGIN
    FOR i := 1 TO 3 DO
        roll := RANDOM(6) + 1;
        InOut.WriteString("Roll "); InOut.WriteInt(i,0); InOut.WriteString(": "); InOut.WriteInt(roll,0); InOut.WriteLn;
    END;
END DiceRoll.

Rolls a six-sided dice three times.

MODULE Countdown;
IMPORT InOut;
VAR count: INTEGER;
BEGIN
    count := 5;
    WHILE count >= 0 DO
        InOut.WriteString("Countdown: "); InOut.WriteInt(count,0); InOut.WriteLn;
        count := count - 1;
    END;
    InOut.WriteString("Done!"); InOut.WriteLn;
END Countdown.

Counts down from 5 to 0.

MODULE PrimeCheck;
IMPORT InOut;
VAR nums: ARRAY 3 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;
        InOut.WriteInt(n,0);
        IF isPrime THEN InOut.WriteString(" is Prime") ELSE InOut.WriteString(" is Not Prime") END;
        InOut.WriteLn;
    END;
END PrimeCheck.

Checks if numbers are prime.

MODULE TempConv;
IMPORT InOut;
VAR c,f: REAL;

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
    InOut.WriteString("25°C = "); InOut.WriteReal(cToF(25),2); InOut.WriteLn;
    InOut.WriteString("77°F = "); InOut.WriteReal(fToC(77),2); InOut.WriteLn;
END TempConv.

Converts Celsius to Fahrenheit and Fahrenheit to Celsius.

MODULE ShoppingCart;
IMPORT InOut;
VAR cart: ARRAY 10 OF ARRAY 50 OF CHAR; prices: ARRAY 10 OF INTEGER; count: INTEGER := 0;

PROCEDURE addItem(item: ARRAY OF CHAR; price: INTEGER);
BEGIN
    cart[count] := item; prices[count] := price; count := count + 1;
    (* print cart and total *)
END addItem;

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

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

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

MODULE Greet;
IMPORT InOut;
PROCEDURE greet(name: ARRAY OF CHAR);
BEGIN
    InOut.WriteString("Hello, "); InOut.WriteString(name); InOut.WriteString("! Welcome!"); InOut.WriteLn;
END greet;

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

Greets users by name.

MODULE Stopwatch;
IMPORT InOut;
VAR time: INTEGER := 0;
BEGIN
    WHILE time < 5 DO
        InOut.WriteString("Stopwatch: "); InOut.WriteInt(time,0); InOut.WriteLn;
        time := time + 1;
    END;
    InOut.WriteString("Done!"); InOut.WriteLn;
END Stopwatch.

Simulates a stopwatch incrementing seconds.