"Controlling complexity is the essence of computer programming."

"Another effective [debugging] technique is to explain your code to someone else. This will often cause you to explain the bug to yourself..."

"Programming language is very specific to instructing a computer to do a particular structure of a sequence. It's the very way you tell the machine what you want it to do."

"Don't comments bad code - rewrite it."

"No matter what, the way to learn to program is to write code and rewrite it and see it used and rewrite again. Reading other people's code is invaluable as well."

"The most effective debugging tool is still careful thought, coupled with judiciously placed print statements."

"Debugging is twice as hard as writing the code in the first place. Therefore, if you wirte the code as cleverly as possible, yu are, by definition, not smart enough to debug it."

(All qoutes above by Brian Kernighan)

 

"Measuring programming progress by lines of code ist like measuring aircraft building progress by weight. (Bill Gates, co-founder Microsoft)

 

"Walking in water and developing Software from a specification are easy if both are frozen." (Edward B. Berard, Software Engineer)

 

What is a computer program?

A program is a sequence of instructions according to the rules of a programming language, with which a task in computer.

Software is an intangible asset and software (no trivial ones) is one of the most complex things people have ever dreamed of.

The error rate in software has steadily decreased in recent years thanks to the use of software engineering and modern software development methods.

The world today cannot exist without software. Software is present as a PC program, as a smartphone app or as embedded software in every complex system. Software is found in infrastructure, industrial production, transportation, finance, film, supermarket checkouts, airport scanners, home appliances, consumer electronics, cars, airplanes, trains and ships, Artificial Intelligence, Internet of Things, Machine Learning, Pattern Recognition, Cognitive Modeling, Natural Language Recognition and Translation, Image Recognition and Processing, Digital Cameras, Smart TVs, Printers, most Automatic machines, in medical diagnostics, in assisted driving and navigation, in weather forecasting, in science and research, e.g. wind tunnel calculations, modeling of nuclear fusion systems, modeling of complex molecules and solving complex mathematical problems.

Software production is also so expensive because hundreds of developers are involved in large software projects and also because the smallest (faulty) changes in the source code can lead to unexpected effects and incorrect functionality of the software and then switch back to the last stable version of the source code (last correct version is fetched from the repository or the last backup is used again), because his quality assurance takes serious resources and also because expensive refactoring is almost always necessary with older software.

The completion of an average individual software costs around 50000€.

Because the source code can be changed so easily, software backup and software versioning play an important role.

The largest software manufacturers worldwide in 2023 are Alphabet - Google ($260 billion in sales), Microsoft ($194 billion in sales), IBM, Accenture, Facebook, Oracle and SAP (largest in Germany).

Software-as-a-Service (SaaS) is the current trend in software usage. With this cloud-based model, end users can access the software online without having to download or update it - the provider is responsible for hosting and maintenance.

Programming methods

  • Structured Programming
  • Modular Programming
  • Object Oriented Programming
  • Event Oriented Programming

Types of software development

  • top down
  • bottom up

Stages of the software development process (Software Development Life Cycle - SDLC)

  • Planning and requirements analysis (define the project scope and objectives, gather and analyze requirements from stakeholders, create a project plan and timeline)
  • Design (develop system architecture and design, create detailed design specifications for components, design user interfaces and user experience - possible use of Computer Aded Software Engineering - CASE tools)
  • Coding or Implementation (write the actual source code based on design specifications, use version control systems to manage codebase, follow coding standards) (1) by one programmer alone (2) by two developers (pair programming) (3) automatically from design specifications
  • Testing and Quality Assurance (1) code reviews: another developer systematically checks the code (2) bug fixing: errors in the code are searched for, found and eliminated (3) testing: the functionality of the software will be checked. Types of tests: static tests, unit tests, integration tests, system tests, user acceptance testing with stakeholders (more and more use of test automation tools)
  • Documentation (1) source code documentation through the use of comments (2) system documentation (3) user documentation (possible automated creation of system documentation from source code)
  • Delivery to the customer (a release of the software will be deployed)
  • Maintenance and care (provide regular updates and patches, implement new features and improvements based on user feedback, later: possible refactoring)
  • Review and Retrospective (analyze the project’s successes and areas for improvement, conduct retrospectives with the development team, implement lessons learned in future projects)

These stages may overlap and iterate in agile methodologies, where continuous feedback and improvements are integral to the process.

In most projects the development is done in a team and therefore the coordination of the work plays an essential role.

The software development life cycle (SDLC) is the process of planning, writing, modifying, and maintaining software. Developers use the methodology as they design and write modern software for computers, cloud deployment, mobile phones, video games, and more. Adhering to the SDLC methodology helps to optimize the final outcome. In IT, the term "life cycle" was first used in the 1950s and 1960s to describe the stages involved in developing a new computer system, but it is now commonly used to refer to all stages in the production of any type of software. These stages of the SDLC are described further up.

The most well-known software development models are:

  • The waterfall model (the phases of software development run sequentially)
  • The V-model
  • The spiral model
  • The incremental and iterative model
  • The Rational Unified Process (RUP)
  • Agile software development (Extreme Programming - XP, Scrum, Kanban)

The best-known Agile models are Scrum and Kanban. Agile software development promises greater transparency and speed of change and faster use of the developed system.

One of the most used graphical modeling languages ​​in the specification and documentation phases of software development is UML (Unified Modeling Language). UML abstracts and visualizes systems of object-oriented programming. UML is therefore a handy tool for developers. On the one hand, it makes it possible to create clear blueprints for software projects, and on the other hand, complex software systems can also be presented in a way that is understandable for non-specialists. With some UML tools (GitMind, Gliffy) diagrams can be converted into a given programming language. They often work with Java, C++, C# or XML schemas. Some tools also reconstruct UML diagrams from existing code.

There's a diference between coding and programming: coding is transforming ideas into a written language that computer can understand, programming is the broader task of determining instruction to give to a computer so it can execute a task. Programming languages are the medium that humans use to "talk" to a machine.

Most programming languages ​​are free of formatting rules as far as the source code is concerned. Despite this, many companies have internal code formatting conventions that all developers must adhere to. This promotes a consistent coding style and ensures good readability of the source code. Code formatting is included as a feature in some IDEs (e.g. Eclipse and Visual Studio) and is applied when generating code. The Emacs and vim editors also offer formatting help. However, there is also stand-alone software, so-called source code formatters (beautifiers) that enable the developer to convert existing source code into a more readable format. In Python, source code formatting is a syntax element, blocks are defined here by their indentation, giving blanks a syntactic meaning.

Version management tools are used in software development (e.g. Git or SVN). Version management offers all developers involved the opportunity to work on a locally cloned version of the project and to compare it with a local version and also to have the source code checked by other developers or automated mechanisms, with the source code being stored in a central repository. In addition to version management, so-called bug trackers are also used.

Behavior-Driven Development (BDD)

In the modern panorama of software development, the BDD approach emerges as a pivotal practice. BDD makes the development process more accessible and understandable for everyone involved, from developers and testers to business stakeholders and other non-technical team members. BDD is a software development approach that extends from Test-Driven Development (TDD). It emphasizes the use of understandable and straightforward language to describe the expected behavior of software. This language is clear and comprehensible to all stakeholders involved, ensuring that everyone is on the same page. BDD is a practice in which testing of program components is used to guide the entire software development process.

Test Driven Development (TDD)

TDD is a design strategy that places testing before creating source code and prioritizes it with respect to operations. The goal is to significantly increase the quality of the software and reduce the maintenance effort afterwards. TDD is mostly used in agile methods and especially in extreme programming.

Programs that translate the code that a programmer writes (source code) into machine language are called compilers and interpreters. The advantage of the interpreter over the compiler is that the same source code can be executed on any target platform. Scripting languages ​​are mostly executed via interpreters, while languages ​​like C or C++ are compiled. Java is a special case, the path from source code to machine code goes through an intermediate step, the so-called Java bytecode (instruction set of the Java Virtual Machine). Thus, on the one hand, one gains the advantage of portability that the interpreter offers, on the other hand, the gain in efficiency through the compiler.

In order to be able to guarantee software quality assurance (QA), the following measures are usually used: specification of code conventions, regular design and code reviews, use of static code analysis tools (these tools can read the source code scan and search for vulnerabilities and can validate source code against company-specific project specifications and ensure project requirements are met - a well-known code analysis tool is SonarQube), using test automation tools (e.g. Selenium or Cucumber), automatically creating system documentation (e.g. with Doxygen), use version control tools (e.g. Git or SVN) and bug trackers.

SOLID is an acronym for Robert C. Martin's First Five Principles of Object Oriented Design (OOD). These principles establish practices appropriate to software development. Adopting these practices can also help avoid code smells, code refactoring, and agile or adaptive software development. SOLID can lead to cleaner, more maintainable and more adaptable code base. SOLID stands for:

  • S - Single Responsibility Principle (principle of clear responsibility)
  • O - Open Closed Principle (principle of openness and closedness)
  • L - Liskov's Substitution Principle
  • I - Interface segregation principle (principle of interface separation)
  • D - Dependency Inversion Principle

Object-Oriented Programming (OOP) was coined by programming legend Alan Kay in the late 1960s. As the name suggests OOP refers to languages that use objects in programming. OOP aims to implement real-world entities like inheritance, hiding and polymorphism in programming. The main aim of OOP is to bind together the data and the functions that operate on them so that no other part of the code can access this data except that function.

OOPs Concepts:

  • Class
  • Objects
  • Data Abstraction 
  • Encapsulation
  • Inheritance
  • Polymorphism
  • Dynamic Binding
  • Message Passing

The class serves as a blueprint for the mapping of real objects into software objects and describes attributes (properties) and methods (behaviors) of the object. Objects are instances of a class created with specially defined data. Methods are functions defined within a class that describe the behavior of an object. Every method contained in class definitions begins with a reference to an instance object. Attributes are defined in the class template and represent the state of an object. The goal of OOP is to increase the flexibility and maintainability of programs. OOP is particularly suitable for large or complex software projects and has the following advantages over other programming models: less error-prone, good reusability and less maintenance.

The frontend is the visible part of software (user interface UI or graphical user interface GUI) with which users can interact. Backend is the part of the software that is not accessible to users.

Refactoring is a central part of agile software development. No sooner has a company released a new version of software than users make new demands for new versions. The range of functions increases over time, but the more extensive and older software and its architecture become, the more difficult it is to further develop it. This is where refactoring helps. It describes the - manual or automated - restructuring of software (usually) while retaining the range of functions.

Legacy software is software that has often been in use for a long time and is no longer technologically up to date. Legacy software usually causes new problems as it gets older, especially if it is operated together with more modern technology. However, there are various reasons why companies often stick with this legacy software: because this old application forms the basis for newer software, because the original developers of the software are no longer available, because this program would not run on current hardware and because an update this old program (refactoring) would not be financially worthwhile.

Current trends in software development are continuous integration (CI) and continuous delivery (CD) and DevOps. DevOps (from the words development and operations). CI ensures that code changes from numerous developers are incorporated into a software project. Functional changes and bug fixes are implemented quickly and sustainably with the CD. DevOps aims to ensure that the areas responsible for the development and operation of the software used in the company and/or by customers work together efficiently.

SourceForge is a web hosting service specialized in hosting open source software. It offers programmers storage space for source code, binary files and a project website. GitHub is also a version control web hosting service for software development projects. The current version of a program is loaded and installed on the computer with a single click. Both Sourceforge and GitHub offer developers the ability to manage their open source programs and download them.

PLC stands for Programmable Logic Controller. PLC is an electronic device that takes over control and regulation tasks in the field of automation technology and PLC programming is the corresponding programming of this device. Well-known PLC software is Siemens Step 7 and CodeSys.

CNC (Computer Numerical Control) programming takes place in manufacturing are used to create program instructions for computers to control machine tools.

Cyber ​​security is measures taken to defend computers, servers, mobile devices, electronic systems, networks and data against malicious attacks. It is also referred to as IT security or electronic data security.This also includes using an antivirus program or virus scanner. This is software that contains malicious programs (malware) e.g. computer viruses, computer worms or trojan horses, block them, inform affected users if necessary and remove the malware. In principle, virus scanners can only detect known malware and therefore cannot protect against all threats.

The term hacker (also computer hacker) usually refers to persons or groups of persons who intrude into external IT systems without authorization. As a hack (or hacking attack), unauthorized access to a third-party device is accordingly named. In addition to criminal hackers or so-called black hat hackers, there are also white hat hackers and gray hat hackers. A white hat hacker (or ethical hacker) is hired by a company to scan systems for security vulnerabilities. To do this, these hackers conduct penetration tests. Penetration tests are simulated repeated cyberattacks on a company's systems.

According to general opinion, a good software developer needs the following qualities (soft skills):

  • team and communication skills
  • empathy (he must be able to put himself in the users' shoes)
  • assertiveness
  • analytical thinking
  • problem-solving skills
  • resilience and flexibility
  • patience
  • creativity
  • humility
  • confidence
  • desire for continuous further education

 

TYPES of SOFTWARE DEVELOPERS

● Senior Developer (more than 5 years of professional experience)
● Junior Developer (career starter)
● Developer specialized in a higher programming language (e.g. C#, C++, Java, JavaScript, Qt, Python, Perl, Ruby, Rust, Scala, Go, Kotlin, Elixir, Angular, ABAP, Next.js, Flutter)
● Full-stack developer (programmer who works in both front-end and back-end development and therefore has expertise in databases, servers, systems and clients. Depending on the client's project, this can be a mobile app, a web app or a native app)
● Software trainer (training in software)
● Software architect (designs the software system, plans it and coordinates its implementation. In doing so, he is in contact with the client)
● System integration developer (mainly installs and sets up software and hardware)
● AI/ML Engineer
● IT Solution Designer
● Front-end developer (UI/UX developer)
● Backend developer
● Desktop Developer
● Mobile App Developer
● Web Developer
● Data Architect
● Database Manager
● Network/Cloud Architect
● DevOps Engineer
● Data Scientist (Big Data Developer)
● Game Developer
● Operating system developer
● System Administrator
● Security Developer
● E-commerce developer

At the end of 2022, there were 27.7 million active software developers worldwide, mostly in the US and Europe.

The average salary for a senior software developer 2020 in the USA is about $92000 and in Germany is €60000.

Code example for a simple program in some languages (writes "Hello World" on the screen):

In C++:

//Hello World! programm                            

#include <iostream>                                          using namespace std;

main()                                                                            {                                                                                            std::cout << "Hello World!" << std::endl;                  return 0;                                                                   }

 

In C#:

//Hello World! programm                                  using System;

public class HelloWorld
{                                                                                            static public void Main ()                                          {
            Console.WriteLine ("Hello World!")                    }                                                                                 }

 

In Java:

//Hello World! programm                                  public class HelloWorld
{
     public static void main (String[] args)                     {
           System.out.println ("Hello World!");                    }                                                                                }

 

In JavaScript:

//Hello World! programm                      

console.log ('Hello World!');

 

In Python:

#Hello World! programm                                      print (“Hello World!”)

 

In Go:                                                             

package main                                                    import "fmt"                                                            func main()                                                                   {                                                                                          fmt.Println ("Hello World!")                                   }

 

Types of software

First classification :

  • System software (programs for controlling hardware - operating systems, programming environments - IDE (Integrated Development Environment))
  • User software or application software (web browser, word processing programs, image editing programs, email software, computer games, virus scanners, apps for smartphones)

Second classification:

  • Packaged or standard software (Microsoft Windows, Microsoft Office, SAP)
  • Open source software (the source code is public)
  • Enterprise software (ERP, CRM)
  • Individual software
  • Embedded software or firmware (is software designed for specific hardware)
  • Cloud-based software (Microsoft 365, Google Workspace)
  • Web applications (run in an Internet browser)

Third classification:

  • Free software (freeware) e.g. Google online services such as Google Chrome, Google Gmail, Google Maps, Google Earth, Google Translate, Google Docs and Android Studio, Mozilla Thunderbird, VLC Media Player, Gimp, Skype, Adobe Acrobat Reader, IrfanView, GRASS GIS, Java, Python, Perl, PHP, Ruby, Qt, Eclipse, many mobile apps and computer games.
  • Open source software (the source code can be viewed) such as the Mozilla Firefox web browser, the Open Office word processing program, the 7-Zip compression program, the Notepad++ text editor, the MySQL database or the Linux operating system (Debian, Ubuntu)
  • Public domain software (The developers of public domain software forego royalties, but the rights and source code remain with the authors)
  • Shareware (free as a test version, demo version or trial, but the full version is only free for a certain period of time and then you have to pay for it), such as WinRAR, WinZip and AutoCAD)
  • Commercial (proprietary) software (paid needed)

Types of programming languages

First classification:

  • Machine languages ​​(consists of the characters 0 and 1 and can be processed directly by the computer)
  • Assembly Languages
  • Higher programming languages ​​(C#, C++, Java, FORTRAN, COBOL, Visual Basic)
  • Scripting languages ​​(Python, Perl, Ruby, JavaScript, TypeScript, PHP, awk)
  • Languages ​​with visual programming environments (DocBook, DITA)
  • Graphic (visual) programming languages ​​(Scratch, Snap!)

Second classification:

  • Imperative languages ​​(BASIC, TurboPascal, C, COBOL, FORTRAN, Ada)
  • Functional languages ​​(LOGO, LISP, Haskell)
  • Predicative (logical) languages ​​(PROLOG)
  • Object-oriented languages ​​(C++, C#, Java, Python, Delphi, VisualBasic, SMALLTALK 80)

Quality features of software

  • Maintainability
  • Functionality
  • User friendliness
  • Efficiency
  • Changeability
  • Verifiability
  • Performance
  • Interoperability/Compatibility
  • Reliability (robustness)
  • Security
  • Portability (transferability)
  • Reusability

History of programming languages

  • Method of programming computers according to the Babbage system, Lovelace, 1843
  • "Plankalkül", Zuse, 1945
  • Algol, 1958
  • LISP, McCarty, 1959
  • COBOL, Hopper, 1960
  • BASIC, Dartmouth College, 1964
  • Simula, Dahl and Nygaard, 1960s
  • SQL, IBM, 1969
  • C, Kernighan and Ritchie, 1969-1973
  • Ada, Ichbiah, 70's
  • Shell, Thompson, 1971
  • Pascal, Wirth, 1971
  • Smalltalk, Xerox PARC, 1972
  • Fortran, IBM, 1975
  • Bourne Shell, Bourne, 1979
  • Turbo Pascal, Hejlsberg, 1983
  • C++, Stroustrup, 1983
  • Perl, Wall, 1987
  • HTML, Berners-Lee, 1989-1990
  • Python, van Rossum, 1991
  • Java, Gosling, 1991
  • JavaScript, Eich, 1995
  • Ruby, Matsumoto, 1995
  • Embedded C++, 1996
  • PHP, Lerdorf, 1997
  • C#, Microsoft, 2000
  • Visual Basic .NET, Microsoft, 2002
  • TypeScript, Microsoft, 2012
  • Go (Golang), 2012, several developers
  • Rust, 2015, Mozilla, Hoare, Rust Foundation
  • Kotlin, 2016, JetBrains

Characterizations of programming languages (1)

  • Assembler (reverse engineering)
  • Bash (Unix shell and command language)
  • Batch (script files in Microsoft Windows)
  • C++ (a very powerful programming language used almost everywhere
  • Java (powerful cross-platform language, native Android programming language)
  • JavaScript (language of the Internet)
  • PHP (also a very powerful and widely used server-side scripting language)
  • PowerShell (command line shell for Microsoft Windows)
  • Python (A very simple, yet powerful high-level programming language)
  • SQL (Almost everything related to databases)
  • Unix Shell (Command language for UNIX)
  • ASP.NET (server-side framework for web applications from Microsoft)
  • C (A lot of computer software and systems written in this language)
  • C# (everything for Microsoft Windows)
  • Haxe (very useful)
  • Lisp (can be used anywhere Python or Ruby is used)
  • Perl (system administration, network programming, finance, bioinformatics and other applications, e.g. for GUIs)
  • Ruby (native language of the Metasploit framework and fun language to learn)
  • ActionScript (Flash and website animation)
  • Swift (iOS programming language)
  • Tcl (used on embedded systems platforms)
  • ActionScript (Flash and website animation)
  • Ada (embedded systems, e.g., avionics, air traffic control, railroads, banking, military, and aerospace)
  • COBOL (used in business, financial, and administrative systems for corporations and governments)
  • Erlang (telecommunications systems and applications such as WhatsApp)
  • Fortran (scientific computing, not as popular as it used to be)
  • Lua (game programming)
  • Objective-C (formerly iOS programming, now replaced by Swift)
  • Pascal (educational purposes)
  • PostScript (printing)
  • Visual Basic (no longer needed in the future)

Characterizations of programming languages (2)

  • C: The boring and correct choice.

  • C++: Thought it was complicated.

  • Objective-C: Now with even more confusing syntax!

  • C#: It's not Java.

  • Swift: It's not JavaScript.

  • Java: The practical choice of middleware developers around the world.

  • Ruby: Because programs should be fun, not efficient!

  • Groovy: Easier than getting Ruby to run in the JVM.

  • Python: Don't choose between functional, procedural and object-oriented styles.

  • PHP: HTML, CSS and SQL inserted and installed everywhere.

  • JavaScript: Single-threaded, natively asynchronous, installed on every modern computer.

  • Go: Priority for type and thread safety.

  • Rust: Much simpler than C, but still with all the syntax errors.

  • Typescript: The Java developer's JavaScript.

  • Elm: Is it like Lisp or not?

  • Clojure: Running the fastest middleware ever developed on the JVM.

  • Schema: Lisp for the 90s.

  • Perl: Free, somewhat overused scripting language. Written once, never debugged.

  • Haskell: The final conclusion on type safety as a design principle.

  • Elixir: What if Ruby took over Haskell and made Erlang run?

Where is the programming language used?

  • Python is a high-level, general-purpose programming language that is widely used in data science, machine learning, artificial intelligence, web development, and scientific computing. It's popularity has grown significantly in recent years due to its simplicity, readability, and versatility. Java is commonly used in web applications, desktop software development, data science and machine learning.
  • Java is a class-based, object-oriented programming language that is commonly used for developing enterprise-level applications, mobile apps, and games. It is known for its stability, security features, and cross-platform compatibility. Java is used on many different devices due to its plat-form independence. In addition to desktop computers, tablets, smartphones, game consoles, TVs and house-hold appliances are also equipped with Java. According to Oracle, Java is used on over 3 billion devices worldwide. Java is heavily used in a variety of software projects and in web development.
  • JavaScript is a client-side scripting language used for creating interactive web pages and applications. It is also used for server-side programming with Node.js. With the rise of web development and the increasing demand for dynamic user interfaces, JavaScript has become one of the most popular programming languages.
  • C# is used in many applications, including programming web applications, mobile apps and computer games.
  • C++ and C are used in programming embedded systems and in game programming.
  • Kotlin is pretty much standard in Android programming. It is a platform-independent, statically typed programming language that can be converted to Java, JavaScript, and machine code. It is therefore very versatile and can be easily integrated into many projects. The integration takes place without any compatibility problems and also requires no interface programming. A big advantage is that the code is compatible with Java. Kotlin offers the same performance as Java with less code.
  • Desktop applications are developed using C#, Java, Swift, Kotlin, C, C++ and Python. For programs that only need to run on Windows, the C# language is often used because it is particularly well integrated with Windows.
  • Java, Kotlin, Swift, Objectiv C and js are preferred for programming mobile apps.
  • Java, Python, PHP, Go, Ruby, Javascript and Kotlin are mostly used for the backend software (software that runs on a server).
  • The most used programming languages ​​2023 are Python, Java, JavaScript, HTML, C# and C++.

Which well-known software was written in which language?

  • In C:            Linux, MS Windows 7
  • In C++:       Apple OS X, MS Office, Mozilla Firefox, MySQL database software, Adobe Photoshop.
  • In C#:         Skype, Sharepoint, MS Visual Studio, most apps in the Windows Store.
  • In Java:      SAP, LinkedIn, Eclipse, MathLab, parts of OpenOffice, NetBeans.
  • In Python:  Google search engine, YouTube, Netflix, Spotify, Instagram, Pinterest.

Integrated Development Environments (IDE) for software developers

An IDE combines developer tools on a central graphical interface.

Examples:

  • Microsoft Visual Studio (C# and Visual Basic)
  • Eclipse (originally developed for Java, can now be used for other languages)
  • Qt Creator (Qt)
  • NetBeans (Java, C++, C)
  • InteliJ (Java, Kotlin)
  • Dev-C++ (C++)
  • Kdevelop (focus on C++)
  • Android Studio (web development)

Frameworks for software developers

Frameworks simplify and accelerate the development and integration of various components and modules.

Examples:

  • Microsoft .NET (typically C#)
  • Microsoft Foundation Classes (GUI creation with C++)
  • WPF (Windows Presentation Foundation) - Microsoft's UI programming for the Windows desktop
  • Qt (platform independent GUI development)
  • Junit (Java)
  • Hibernate (Java)
  • AngularJS (web development)
  • Angular (web development)
  • Spring (web development)
  • React (web development)
  • Ruby on Rails (web development)
  • Django (web development)
  • Selenium (web application testing)
  • Microsoft Azure (cloud platform)
  • Google Cloud (cloud platform)

Number of source code lines of well-known software

  • Operating system Unix, 1971 (20000 lines)
  • Simple game app (50000 lines)
  • Computer game Minecraft (285000 lines)
  • Computer game "Age of Empires" (2 million lines)
  • Hubble telescope software (2 million lines)
  • Space Shuttle software (3 million lines)
  • Mars Curiosity rover software (5 million lines)
  • Boeing 787 flight software (6 million lines)
  • Android operating system (12 million lines)
  • Operating system Linux 3.2, 2012 (15 million lines)
  • Mozilla Firefox web browser (22 million lines)
  • IDE Visual Studio 2012 (50 million rows)
  • CERN Large Hadron Collider software (50 million lines)
  • Microsoft Windows 7 operating system (40 million lines)
  • Facebook (62 million rows)
  • Operating system Apple Mac OS Tiger (85 million lines)
  • Software of the VW Golf 8 (100 million lines)
  • SAP NetWeaver, 2007 (238 million rows)
  • All Internet services from Google (2 billion lines)

Software errors (bugs)

Software has now become so complex that it is no longer possible to control all influences on software reliability and to achieve complete freedom from errors (no bugs).

With enough time and money, software can be tested to a specified level of security, but this effort quickly reaches economically justifiable limits. In addition, today's software development has become a dynamic process in which many individual components are developed in parallel.

The aim is to be able to make a statement about the stability of the later software very early in the development phase. This aspect is of particular interest to quality managers who want to get to the bottom of possible software reliability deficiencies in their company.

On average there are 1 to 3 residual errors per 1000 lines of source code.

In general, the guiding principle applies: The earlier in a development process the error occurs and the later it is discovered, the more complex it is to fix the error.

One piece of software that has been particularly scrutinized is that of the NASA Space Shuttle: it is estimated that only 300 errors remain in its 3 million lines of source code.

Types of software errors (bugs)

  • lexical errors (e.g. unknown reference)
  • syntactic errors (e.g. forgotten semicolon)
  • semantic errors (incorrect declaration)
  • runtime error (wrongly formatted input data)
  • logical errors (e.g. plus instead of minus, loop errors)

Famous software bugs and computer attacks

  • Typo in the source code, 1962 (loss of the NASA satellite Mariner I)
  • Software error caused by counter overflow, Bank of New-York, 1985 (securities transaction stopped causing $5 million in interest loss in one day)
  • Bugs in new software at AT&T, 1990 (60000 people could not make long distance calls for 6 hours)
  • Pentium processor division error, Intel, 1994 ($475 million additional cost to replace processor)
  • Computer crash due to insufficiently dimensioned stack memory, railway signal box Hamburg, 1995 (unintentional closing of the signal box)
  • Existing program code of the Ariane 4 rocket taken over, 1996 (loss of the Ariane 5 rocket)
  • English to metric unit conversion error in program code, 1999 (loss of NASA Mars orbiter)
  • Date error due to counter overflow (year 2000-Y2K bug, year 2038 on Unix systems, went prett lightly)
  • Missing compatibility of software modules, Toll Collect, 2003 (billions of dollars in lost revenue)
  • Obamacare software swallows a third of insurance applications, 2010
  • Private data shared by six million social network mem-bers, 2013
  • Macro computer virus (malware) and e-mail worm for Outlook "Melissa" infected many computers, 1999, USA and part of Europe ($1.1 billion damage)
  • "I love You" computer worm, 2000 (brought many Outlook servers to their knees - damage of $3 billion)
  • Computer worm "MyDom" infected around 300,000 computers in 2004 (damage of over $30 billion)
  • "Stuxnet" computer worm, 2010 (One of its more aggressive variants later infected 6 million computers via the Internet in China alone)