Learn Eiffel - 10 Code Examples & CST Typing Practice Test

Eiffel is a high-level, object-oriented programming language designed for software engineering with a strong emphasis on correctness, reusability, and maintainability. It supports the Design by Contract methodology, promoting robust and reliable applications.

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Eiffel Counter and Theme Toggle Eiffel Fibonacci Sequence Eiffel Factorial Calculator Eiffel Prime Checker Eiffel Sum of Array Eiffel Reverse String Eiffel Multiplication Table Eiffel Temperature Converter Eiffel Simple Alarm Simulation Eiffel Random Walk Simulation

Learn EIFFEL with Real Code Examples

Updated Nov 20, 2025

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Code Sample Descriptions

Eiffel Counter and Theme Toggle

class
    COUNTER
feature
    count: INTEGER
    is_dark: BOOLEAN

    update_ui
        do
        io.put_string ("Counter: " + count.out + '\n')
        io.put_string ("Theme: " + (if is_dark then "Dark" else "Light") + '\n')
        end

    increment
        do
        count := count + 1
        update_ui
        end

    decrement
        do
        count := count - 1
        update_ui
        end

    reset
        do
        count := 0
        update_ui
        end

    toggle_theme
        do
        is_dark := not is_dark
        update_ui
        end
end

! Simulate actions
local
    c: COUNTER
do
    create c
    c.update_ui
    c.increment
    c.increment
    c.toggle_theme
    c.decrement
    c.reset
end

Demonstrates a simple counter with theme toggling using Eiffel classes and methods.

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Eiffel Fibonacci Sequence

class
    FIBONACCI
feature
    compute
        do
        local a, b, c, i: INTEGER
        a := 0
        b := 1
        io.put_integer(a); io.put_new_line
        io.put_integer(b); io.put_new_line
        from i := 1 until i > 8 loop
        c := a + b
        io.put_integer(c); io.put_new_line
        a := b
        b := c
        i := i + 1
        end
        end
end

! Run
local
    f: FIBONACCI
do
    create f
    f.compute
end

Generates first 10 Fibonacci numbers.

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Eiffel Factorial Calculator

class
    FACTORIAL
feature
    compute (n: INTEGER)
        local f, i: INTEGER
        do
        f := 1
        from i := 1 until i > n loop
        f := f * i
        i := i + 1
        end
        io.put_string ("Factorial: "); io.put_integer(f); io.put_new_line
        end
end

! Run
local
    fact: FACTORIAL
do
    create fact
    fact.compute(5)
end

Calculates factorial of a given number.

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Eiffel Prime Checker

class
    PRIME_CHECKER
feature
    is_prime (n: INTEGER): BOOLEAN
        local i: INTEGER
        do
        from i := 2 until i >= n loop
        if n \ i = 0 then
        Result := False
        return
        end
        i := i + 1
        end
        Result := True
        end
end

! Run
local
    p: PRIME_CHECKER
    num: INTEGER
do
    num := 13
    create p
    if p.is_prime(num) then
        io.put_string ("Prime"); io.put_new_line
    else
        io.put_string ("Not Prime"); io.put_new_line
    end
end

Checks if a number is prime.

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Eiffel Sum of Array

class
    ARRAY_SUM
feature
    sum_array (arr: ARRAY[INTEGER])
        local total, i: INTEGER
        do
        total := 0
        from i := arr.lower until i > arr.upper loop
        total := total + arr[i]
        i := i + 1
        end
        io.put_string ("Sum: "); io.put_integer(total); io.put_new_line
        end
end

! Run
local
    a: ARRAY_SUM
    arr: ARRAY[INTEGER]
    i: INTEGER
do
    create a
    create arr.make(1,5)
    arr[1] := 1; arr[2] := 2; arr[3] := 3; arr[4] := 4; arr[5] := 5
    a.sum_array(arr)
end

Calculates the sum of an array of integers.

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Eiffel Reverse String

class
    REVERSE_STRING
feature
    reverse (s: STRING)
        local i: INTEGER; result: STRING
        do
        create result.make_empty
        from i := s.count until i = 0 loop
        result.append_character(s[i])
        i := i - 1
        end
        io.put_string(result); io.put_new_line
        end
end

! Run
local
    r: REVERSE_STRING
    s: STRING
do
    create r
    s := "Hello"
    r.reverse(s)
end

Reverses a string.

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Eiffel Multiplication Table

class
    MULT_TABLE
feature
    print_table (n: INTEGER)
        local i: INTEGER
        do
        from i := 1 until i > 10 loop
        io.put_integer(n); io.put_string (" x "); io.put_integer(i); io.put_string (" = "); io.put_integer(n * i); io.put_new_line
        i := i + 1
        end
        end
end

! Run
local
    t: MULT_TABLE
do
    create t
    t.print_table(5)
end

Prints the multiplication table of a number.

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Eiffel Temperature Converter

class
    TEMP_CONVERTER
feature
    c_to_f (c: REAL)
        local f: REAL
        do
        f := (c * 9.0 / 5.0) + 32.0
        io.put_real(f); io.put_new_line
        end
end

! Run
local
    t: TEMP_CONVERTER
do
    create t
    t.c_to_f(25.0)
end

Converts Celsius to Fahrenheit.

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Eiffel Simple Alarm Simulation

class
    ALARM_SIMULATION
feature
    check_temperature (temp, threshold: INTEGER)
        do
        if temp > threshold then
        io.put_string("Alarm: Temperature Too High!"); io.put_new_line
        else
        io.put_string("Temperature Normal"); io.put_new_line
        end
        end
end

! Run
local
    a: ALARM_SIMULATION
do
    create a
    a.check_temperature(80, 75)
end

Simulates a simple alarm when a threshold is reached.

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Eiffel Random Walk Simulation

class
    RANDOM_WALK
feature
    simulate (steps: INTEGER)
        local i, position: INTEGER
        do
        position := 0
        from i := 1 until i > steps loop
        if random(2) = 0 then
        position := position + 1
        else
        position := position - 1
        end
        io.put_integer(position); io.put_new_line
        i := i + 1
        end
        end
end

! Run
local
    rw: RANDOM_WALK
do
    create rw
    rw.simulate(10)
end

Simulates a random walk using integers.

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Frequently Asked Questions about Eiffel

What is Eiffel?

What are the primary use cases for Eiffel?

High-reliability enterprise software. Safety-critical systems. Reusable component libraries. Formal software engineering projects. Educational use for software engineering principles

What are the strengths of Eiffel?

Encourages correct and maintainable code. Supports formal software engineering methodologies. Highly reusable libraries via genericity. Robust exception handling and error detection. Object-oriented features fully integrated with contract-based programming

What are the limitations of Eiffel?

Smaller developer community compared to mainstream languages. Limited third-party libraries and ecosystem. Less industry adoption for modern web/mobile applications. Verbose syntax for simple tasks. Learning curve for Design by Contract concepts

How can I practice Eiffel typing speed?

CodeSpeedTest offers 10+ real Eiffel 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

Eiffel Counter and Theme Toggle

class
    COUNTER
feature
    count: INTEGER
    is_dark: BOOLEAN

    update_ui
        do
        io.put_string ("Counter: " + count.out + '\n')
        io.put_string ("Theme: " + (if is_dark then "Dark" else "Light") + '\n')
        end

    increment
        do
        count := count + 1
        update_ui
        end

    decrement
        do
        count := count - 1
        update_ui
        end

    reset
        do
        count := 0
        update_ui
        end

    toggle_theme
        do
        is_dark := not is_dark
        update_ui
        end
end

! Simulate actions
local
    c: COUNTER
do
    create c
    c.update_ui
    c.increment
    c.increment
    c.toggle_theme
    c.decrement
    c.reset
end

Demonstrates a simple counter with theme toggling using Eiffel classes and methods.

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Eiffel Fibonacci Sequence

class
    FIBONACCI
feature
    compute
        do
        local a, b, c, i: INTEGER
        a := 0
        b := 1
        io.put_integer(a); io.put_new_line
        io.put_integer(b); io.put_new_line
        from i := 1 until i > 8 loop
        c := a + b
        io.put_integer(c); io.put_new_line
        a := b
        b := c
        i := i + 1
        end
        end
end

! Run
local
    f: FIBONACCI
do
    create f
    f.compute
end

Generates first 10 Fibonacci numbers.

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Eiffel Factorial Calculator

class
    FACTORIAL
feature
    compute (n: INTEGER)
        local f, i: INTEGER
        do
        f := 1
        from i := 1 until i > n loop
        f := f * i
        i := i + 1
        end
        io.put_string ("Factorial: "); io.put_integer(f); io.put_new_line
        end
end

! Run
local
    fact: FACTORIAL
do
    create fact
    fact.compute(5)
end

Calculates factorial of a given number.

Let’s Try →

Eiffel Prime Checker

class
    PRIME_CHECKER
feature
    is_prime (n: INTEGER): BOOLEAN
        local i: INTEGER
        do
        from i := 2 until i >= n loop
        if n \ i = 0 then
        Result := False
        return
        end
        i := i + 1
        end
        Result := True
        end
end

! Run
local
    p: PRIME_CHECKER
    num: INTEGER
do
    num := 13
    create p
    if p.is_prime(num) then
        io.put_string ("Prime"); io.put_new_line
    else
        io.put_string ("Not Prime"); io.put_new_line
    end
end

Checks if a number is prime.

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Eiffel Sum of Array

class
    ARRAY_SUM
feature
    sum_array (arr: ARRAY[INTEGER])
        local total, i: INTEGER
        do
        total := 0
        from i := arr.lower until i > arr.upper loop
        total := total + arr[i]
        i := i + 1
        end
        io.put_string ("Sum: "); io.put_integer(total); io.put_new_line
        end
end

! Run
local
    a: ARRAY_SUM
    arr: ARRAY[INTEGER]
    i: INTEGER
do
    create a
    create arr.make(1,5)
    arr[1] := 1; arr[2] := 2; arr[3] := 3; arr[4] := 4; arr[5] := 5
    a.sum_array(arr)
end

Calculates the sum of an array of integers.

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Eiffel Reverse String

class
    REVERSE_STRING
feature
    reverse (s: STRING)
        local i: INTEGER; result: STRING
        do
        create result.make_empty
        from i := s.count until i = 0 loop
        result.append_character(s[i])
        i := i - 1
        end
        io.put_string(result); io.put_new_line
        end
end

! Run
local
    r: REVERSE_STRING
    s: STRING
do
    create r
    s := "Hello"
    r.reverse(s)
end

Reverses a string.

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Eiffel Multiplication Table

class
    MULT_TABLE
feature
    print_table (n: INTEGER)
        local i: INTEGER
        do
        from i := 1 until i > 10 loop
        io.put_integer(n); io.put_string (" x "); io.put_integer(i); io.put_string (" = "); io.put_integer(n * i); io.put_new_line
        i := i + 1
        end
        end
end

! Run
local
    t: MULT_TABLE
do
    create t
    t.print_table(5)
end

Prints the multiplication table of a number.

Let’s Try →

Eiffel Temperature Converter

class
    TEMP_CONVERTER
feature
    c_to_f (c: REAL)
        local f: REAL
        do
        f := (c * 9.0 / 5.0) + 32.0
        io.put_real(f); io.put_new_line
        end
end

! Run
local
    t: TEMP_CONVERTER
do
    create t
    t.c_to_f(25.0)
end

Converts Celsius to Fahrenheit.

Let’s Try →

Eiffel Simple Alarm Simulation

class
    ALARM_SIMULATION
feature
    check_temperature (temp, threshold: INTEGER)
        do
        if temp > threshold then
        io.put_string("Alarm: Temperature Too High!"); io.put_new_line
        else
        io.put_string("Temperature Normal"); io.put_new_line
        end
        end
end

! Run
local
    a: ALARM_SIMULATION
do
    create a
    a.check_temperature(80, 75)
end

Simulates a simple alarm when a threshold is reached.

Let’s Try →

Eiffel Random Walk Simulation

class
    RANDOM_WALK
feature
    simulate (steps: INTEGER)
        local i, position: INTEGER
        do
        position := 0
        from i := 1 until i > steps loop
        if random(2) = 0 then
        position := position + 1
        else
        position := position - 1
        end
        io.put_integer(position); io.put_new_line
        i := i + 1
        end
        end
end

! Run
local
    rw: RANDOM_WALK
do
    create rw
    rw.simulate(10)
end

Simulates a random walk using integers.

Let’s Try →

Frequently Asked Questions about Eiffel

What is Eiffel?

What are the primary use cases for Eiffel?

High-reliability enterprise software. Safety-critical systems. Reusable component libraries. Formal software engineering projects. Educational use for software engineering principles

What are the strengths of Eiffel?

What are the limitations of Eiffel?

How can I practice Eiffel typing speed?

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