Learn ALGOL with Real Code Examples

begin
    integer count;
    boolean isDark;

    count := 0;
    isDark := false;

    procedure updateUI;
    begin
        print("Counter: ", count);
        print("Theme: ", if isDark then "Dark" else "Light");
    end;

    procedure increment;
    begin
        count := count + 1;
        updateUI;
    end;

    procedure decrement;
    begin
        count := count - 1;
        updateUI;
    end;

    procedure reset;
    begin
        count := 0;
        updateUI;
    end;

    procedure toggleTheme;
    begin
        isDark := not isDark;
        updateUI;
    end;

    comment Simulate actions;
    updateUI;
    increment;
    increment;
    toggleTheme;
    decrement;
    reset;
end

Demonstrates a simple counter with theme toggling using ALGOL-style structured programming.

begin
    integer a, b, c, i;
    a := 0;
    b := 1;
    print(a);
    print(b);

    for i := 1 step 1 until 8 do
    begin
        c := a + b;
        print(c);
        a := b;
        b := c;
    end;
end

Generates the first 10 Fibonacci numbers.

begin
    integer n, f, i;
    n := 5;
    f := 1;
    for i := 1 step 1 until n do
    begin
        f := f * i;
    end;
    print(f);
end

Calculates the factorial of a number.

begin
    integer num, i;
    boolean isPrime;
    num := 13;
    isPrime := true;
    for i := 2 step 1 until num-1 do
    begin
        if num mod i = 0 then
        begin
        isPrime := false;
        goto end_loop;
        end;
    end;
end_loop:
    if isPrime then print("Prime") else print("Not Prime");
end

Checks if a number is prime.

begin
    integer arr[5], sum, i;
    arr[1] := 1; arr[2] := 2; arr[3] := 3; arr[4] := 4; arr[5] := 5;
    sum := 0;
    for i := 1 step 1 until 5 do
        sum := sum + arr[i];
    print(sum);
end

Calculates the sum of an integer array.

begin
    string s, r;
    integer i;
    s := "Hello";
    r := "";
    for i := length(s) step -1 until 1 do
        r := r + s[i];
    print(r);
end

Reverses a string character by character.

begin
    integer n, i;
    n := 5;
    for i := 1 step 1 until 10 do
        print(n, " x ", i, " = ", n*i);
end

Prints multiplication table of a number.

begin
    real c, f;
    c := 25.0;
    f := (c * 9.0 / 5.0) + 32.0;
    print(f);
end

Converts Celsius to Fahrenheit.

begin
    integer temperature, threshold;
    temperature := 80;
    threshold := 75;
    if temperature > threshold then
        print("Alarm: Temperature Too High!")
    else
        print("Temperature Normal");
end

Simulates an alarm when a threshold is reached.

begin
    integer steps, i, position;
    steps := 10;
    position := 0;
    for i := 1 step 1 until steps do
    begin
        if random(2) = 0 then
        position := position + 1
        else
        position := position - 1;
        print(position);
    end;
end

Simulates a 1D random walk using integers.