Skip to main content
CodeSpeedTest
Languages
Start TypingJump into a test — pick any languageAdaptive TrainingUnlock chars as you master themPractice DrillsFocused sessions targeting weak spotsDaily ChallengesNew coding challenges every dayRace ModeCompete against others in real timeAI OpponentRace against an AI at your WPM levelTournamentsLive coding speed tournamentsArcade GamesZType, Overkill Survival, Glyphica & moreGamificationXP, coins, badges & quests
LeaderboardGlobal rankings for every languageCertificatesEarn verifiable Bronze / Silver / Gold certsActivityDaily streaks & historical analyticsProfileYour stats, badges & achievements
Browse Languages500+ languages with real code examplesBlogTips, guides & deep divesFree ToolsWPM calculator, typing speed report & moreFAQCommon questions answeredGetting StartedNew to CodeSpeedTest?AboutOur story & missionSupportGet help — Pro users get priorityContactGet in touch with the team
Pricing
  1. Home
  2. /
  3. Learn
  4. /
  5. Eiffel

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.

View all 10 Eiffel code examples →
Eiffel Counter and Theme ToggleEiffel Fibonacci SequenceEiffel Factorial CalculatorEiffel Prime CheckerEiffel Sum of ArrayEiffel Reverse StringEiffel Multiplication TableEiffel Temperature ConverterEiffel Simple Alarm SimulationEiffel Random Walk Simulation

Learn EIFFEL with Real Code Examples

Updated Nov 20, 2025

Explain

Eiffel enforces object-oriented principles such as classes, inheritance, polymorphism, and genericity.

Design by Contract allows developers to specify preconditions, postconditions, and invariants for software correctness.

Used for building complex systems, safety-critical applications, and reusable libraries.

Core Features

Classes, objects, and inheritance

Preconditions, postconditions, invariants

Genericity for reusable components

Deferred (abstract) and effective (concrete) classes

Exception handling and assertions

Basic Concepts Overview

Classes, objects, and references

Features (methods) and attributes

Preconditions, postconditions, invariants

Generic classes

Inheritance and polymorphism

Project Structure

Class files (.e)

Library or module folders

Project configuration files

Generated binaries or executable

Documentation and contract specifications

Building Workflow

Design class hierarchy and contracts

Implement classes and features

Compile with Eiffel compiler

Run and test with assertions enabled

Refactor and extend with reusable components

Difficulty Use Cases

Beginner: simple classes and objects

Intermediate: inheritance and genericity

Advanced: large-scale systems with contracts

Expert: safety-critical and mission-critical applications

Comparisons

Higher emphasis on correctness than Java or C++

Integrated contract system vs external testing

Object-oriented like C++ or Java, but with design-by-contract

Less widespread than mainstream languages

Focus on software engineering rigor

Versioning Timeline

1985 - Initial Eiffel design by Bertrand Meyer

1987 - First Eiffel compiler released

1990s - EiffelStudio development and evolution

2000s - Improved OO support and libraries

2010s-2025 - Modern EiffelStudio with updated libraries and tools

Glossary

Feature: method or attribute of a class

Class: blueprint for objects

Precondition: condition before method execution

Postcondition: condition after method execution

Invariant: condition always true for class

Installation Setup

Install EiffelStudio IDE or compatible compiler

Set up project workspace

Create new Eiffel project

Configure compiler options and target platform

Compile and run sample Eiffel programs

Environment Setup

Install EiffelStudio IDE

Set up project workspace

Configure compiler paths

Create new Eiffel project

Compile and test sample programs

Config Files

Project.ecf - Eiffel configuration file

Library files (.e) for classes

Compiled binary outputs

Documentation and contract files

IDE-specific settings

Cli Commands

ec -compile project.ecf

ec -run project

ec -check project.ecf

ec -test project

ec -doc project

Internationalization

Supports Unicode strings

Contracts and messages can be localized

EiffelVision supports multi-language UI

Date and number formats can be locale-specific

Documentation can be translated

Accessibility

EiffelStudio IDE supports accessibility

Contracts and assertions help debugging

Documentation embedded in code

Community resources for learning

Step-through debugging available

Ui Styling

GUI via EiffelVision toolkit

Window, widgets, buttons, and menus

Event-driven interactions

Cross-platform support for GUI

Contract-driven GUI behavior

State Management

Object instances hold state

Class invariants enforce consistent state

Attributes and references track program data

Immutable objects can be used for safety

Contract checks enforce correct state transitions

Data Management

Attributes store object data

Collections via generic classes

File or database interaction via libraries

Serialization through Eiffel libraries

Contracts enforce valid data

Architecture

Class-based object-oriented architecture

Separation of deferred (abstract) and effective (concrete) classes

Contracts embedded in code for runtime checks

Inheritance and polymorphism for extensibility

Garbage-collected runtime environment

Rendering Model

Eiffel source code

Compiled via EiffelStudio or compatible compiler

Run as native executable or library

Assertions checked during runtime

Supports integration with other systems and GUIs

Architectural Patterns

Class-based OO architecture

Design by Contract embedded in classes

Generic reusable components

Multiple inheritance with controlled resolution

Event-driven and modular software design

Real World Architectures

Enterprise business applications

Safety-critical embedded systems

Reusable libraries for multiple projects

Simulation and modeling tools

GUI applications with EiffelVision

Design Principles

Design by Contract

Strong typing with static checks

Object-oriented design

Emphasis on reusability and maintainability

Robust error detection via contracts

Scalability Guide

Use generic classes for reusable components

Modularize classes for large projects

Optimize contracts to minimize runtime overhead

Leverage Eiffel libraries for standard patterns

Integrate with other languages for performance-critical parts

Migration Guide

Port legacy OO code to Eiffel with contracts

Refactor procedural code into classes

Convert untyped scripts into strongly typed Eiffel programs

Integrate with C/C++ modules if needed

Use EiffelStudio tools to modernize projects

Performance Notes

Compile with optimization flags

Avoid excessive contract checks in production

Use efficient data structures

Leverage Eiffel generics for reuse

Minimize unnecessary object creation

Security Notes

Ensure contracts cover all edge cases

Validate input data rigorously

Use exception handling to maintain system integrity

Restrict access to sensitive methods

Follow secure coding practices in contracts

Monitoring Analytics

Runtime contract violation logs

EiffelStudio debugger

Unit test coverage reports

Performance profiling tools

Exception handling monitoring

Code Quality

Use Design by Contract extensively

Document classes and features

Write modular and reusable code

Unit test features with EiffelUnit

Refactor regularly to maintain invariants

Practical Examples

Bank account management system with contracts

Inventory management with inheritance

Reusable generic container library

GUI applications using EiffelVision

Safety-critical simulation modules

Troubleshooting

Check contract violations during runtime

Validate inheritance and feature resolution

Verify compilation with Eiffel compiler

Review generic type parameters

Use IDE debugger for feature execution

Testing Guide

Enable assertions to test contracts

Use EiffelUnit for unit testing

Validate preconditions and postconditions

Test inheritance hierarchies

Stress-test reusable components

Deployment Options

Compile to native executables

Package libraries for reuse

Deploy GUI apps with EiffelVision runtime

Embed in larger multi-language systems

Deploy safety-critical modules with verification

Tools Ecosystem

EiffelStudio IDE

SmartEiffel compiler

ISE Eiffel libraries

EiffelBuild tools

EiffelVision GUI toolkit

Integrations

Integration with C/C++ libraries

COM or .NET interoperability

Database connectivity via Eiffel libraries

Web services interaction

EiffelVision for GUI applications

Productivity Tips

Leverage EiffelStudio templates

Reuse generic classes

Write contracts for all critical features

Use unit tests extensively

Document invariants and assumptions

Challenges

Implement a bank account system with preconditions

Create a generic container library

Develop a small GUI app with EiffelVision

Refactor code to maximize contract coverage

Build a safety-critical module

Learning Path

Learn basic OO principles

Understand Eiffel syntax and class structure

Master Design by Contract methodology

Practice with EiffelStudio IDE

Build reusable components and libraries

Skill Improvement Plan

Week 1: Basic classes and objects

Week 2: Contracts and assertions

Week 3: Inheritance and polymorphism

Week 4: Generic classes and reusable libraries

Interview Questions

What is Design by Contract in Eiffel?

How does Eiffel support multiple inheritance?

Explain generic classes in Eiffel.

How are preconditions, postconditions, and invariants used?

What is EiffelVision and its purpose?

Cheat Sheet

class ACCOUNT

feature

deposit(amount: REAL)

require amount > 0

ensure balance = old balance + amount

Books

Object-Oriented Software Construction by Bertrand Meyer

Eiffel: The Language

Programming in Eiffel

Tutorials

EiffelStudio Getting Started

Eiffel Tutorial for Beginners

EiffelVision GUI Tutorial

Official Docs

EiffelStudio Documentation

Design by Contract Reference

Eiffel Language Standard

Community Links

EiffelForum

StackOverflow Eiffel tag

GitHub Eiffel projects

Community Support

Eiffel Forum

EiffelStudio user community

StackOverflow Eiffel tag

GitHub Eiffel projects

Academic papers and university courses

Monetization

Enterprise software development

Safety-critical application contracts

Consulting for reliable system design

Reusable library distribution

Educational and academic usage

Future Roadmap

Modern EiffelStudio IDE improvements

Integration with modern GUI and web frameworks

Enhanced Eiffel libraries and components

Better tooling for testing and debugging

Continued focus on software correctness and reliability

When Not To Use

Small scripting tasks

Modern mobile app development

Rapid prototyping for web

Highly dynamic or loosely typed systems

Projects with tight integration with mainstream ecosystems without Eiffel libraries

Final Summary

Eiffel is a rigorously designed OO language for correctness, maintainability, and reusability.

Its Design by Contract methodology enforces reliability in software systems.

Used in high-reliability, enterprise, and safety-critical applications.

Less mainstream but highly valued for software engineering best practices.

Faq

Is Eiffel still relevant?

Yes - for software engineering and high-reliability systems.

Can Eiffel integrate with other languages?

Yes - C/C++, COM, .NET, and web services.

Does Eiffel support OO fully?

Yes - classes, inheritance, polymorphism, and generics are all supported.

What is Design by Contract?

A methodology to enforce correctness via preconditions, postconditions, and invariants.

Code Sample Descriptions

1

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.

Let’s Try →
2

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.

Let’s Try →
3

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 →
4

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.

Let’s Try →
5

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.

Let’s Try →
6

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.

Let’s Try →
7

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 →
8

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 →
9

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 →
10

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?

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.

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.

Learn Other Programming Languages

CReactPythonC++RustTypeScriptKotlinPHPJavaC#RubyMqlCqlN1qlCypherGremlinPartiqlHaskellElixirFsharpView all languages →
CodeSpeedTest

Improve your coding speed, code accuracy, and programming syntax WPM with practice sessions across 500+ programming languages.

Quick Links

HomeAboutFeaturesGetting StartedLanguages

Legal & Support

Pro ⚡ PricingContactPrivacy PolicyTerms of Service

Connect

CodeSpeedTest on GitHubCodeSpeedTest on TwitterEmail CodeSpeedTest

© 2026 CodeSpeedTest. All rights reserved.