Learn MODULA with Real Code Examples

# modula2/demo.m2
MODULE Counter;
IMPORT InOut;
BEGIN
    FOR i := 1 TO 5 DO
        InOut.WriteInt(i, 0);
        InOut.WriteLn;
    END;
END Counter.

A simple Modula-2 program printing numbers 1 to 5.

# modula3/demo.m3
MODULE Counter;
IMPORT IO;
BEGIN
    FOR i := 1 TO 5 DO
        IO.Put(i);
        IO.PutChar('\n');
    END;
END Counter.

A simple Modula-3 program printing numbers 1 to 5.

# modula2/fib.m2
MODULE Fibonacci;
IMPORT InOut;
VAR a, b, tmp, i: INTEGER;
BEGIN
    a := 0; b := 1;
    FOR i := 1 TO 10 DO
        InOut.WriteInt(a, 0);
        InOut.WriteLn;
        tmp := a + b;
        a := b;
        b := tmp;
    END;
END Fibonacci.

Calculates and prints Fibonacci numbers up to 10.

# modula3/factorial.m3
MODULE Factorial;
IMPORT IO;
VAR n, fact, i: INTEGER;
BEGIN
    n := 5; fact := 1;
    FOR i := 1 TO n DO
        fact := fact * i;
    END;
    IO.Put(fact);
    IO.PutChar('\n');
END Factorial.

Calculates factorial of 5 and prints the result.

# modula2/array_sum.m2
MODULE ArraySum;
IMPORT InOut;
VAR arr: ARRAY 1..5 OF INTEGER := (1,2,3,4,5);
    sum, i: INTEGER;
BEGIN
    sum := 0;
    FOR i := 1 TO 5 DO
        sum := sum + arr[i];
    END;
    InOut.WriteInt(sum,0);
    InOut.WriteLn;
END ArraySum.

Sums elements of an integer array.

# modula3/while_loop.m3
MODULE WhileDemo;
IMPORT IO;
VAR i: INTEGER;
begin
    i := 1;
    WHILE i <= 5 DO
        IO.Put(i);
        IO.PutChar('\n');
        i := i + 1;
    END;
END WhileDemo.

Prints numbers from 1 to 5 using a WHILE loop.

# modula2/if_example.m2
MODULE EvenOdd;
IMPORT InOut;
VAR n: INTEGER;
BEGIN
    n := 7;
    IF n MOD 2 = 0 THEN
        InOut.WriteString("Even");
    ELSE
        InOut.WriteString("Odd");
    END;
    InOut.WriteLn;
END EvenOdd.

Checks if a number is even or odd.

# modula3/double.m3
MODULE DoubleFunc;
IMPORT IO;
PROCEDURE Double(x: INTEGER): INTEGER;
BEGIN
    RETURN 2*x;
END Double;

BEGIN
    IO.Put(Double(5));
    IO.PutChar('\n');
END DoubleFunc.

Defines a function to double a number and prints the result.

# modula2/mult_table.m2
MODULE Table;
IMPORT InOut;
VAR i,j: INTEGER;
BEGIN
    FOR i := 1 TO 5 DO
        FOR j := 1 TO 5 DO
        InOut.WriteInt(i*j,0);
        InOut.WriteString(" ");
        END;
        InOut.WriteLn;
    END;
END Table.

Prints a 5x5 multiplication table.

# modula3/record.m3
MODULE PointDemo;
IMPORT IO;
TYPE Point = RECORD x,y: INTEGER END;
VAR p: Point;
BEGIN
    p.x := 10; p.y := 20;
    IO.Put(p.x);
    IO.PutChar(',');
    IO.Put(p.y);
    IO.PutChar('\n');
END PointDemo.

Defines a record type for a point and prints its coordinates.