¶ Fortran
¶ Programming Languages
For more than six decades, Fortran has carried the weight of some of humanity’s most ambitious ideas—scientific breakthroughs, engineering marvels, and the numerical heavy lifting behind countless simulations. It’s a language with a long memory and an impressively steady pulse. While many newer languages come and go in bursts of popularity, Fortran continues to thrive quietly in research labs, aerospace projects, climate modeling centers, and high-performance computing clusters around the world. It’s the kind of language that rarely makes headlines, but relentlessly powers the discoveries that do.
This course of one hundred articles is designed to guide you through that world—not in a rushed, superficial way, but through a thoughtful exploration of how Fortran works, why it remains relevant, and how to write modern, elegant, and efficient Fortran code. Whether you’re a scientist who wants to dive deeper into numerical computing, a programmer curious about a language with a rich history, or a student aiming to expand your understanding of compiled languages, you will find something here that both resonates with your experience and expands your skillset.
Many people approach Fortran with assumptions: that it’s outdated, that it’s “only for old mainframes,” or that it’s been eclipsed by languages like C++, Python, or Julia. The irony is that Fortran is still one of the fastest and most practical tools available for performance-intensive tasks. When you peel back the layers, you’ll find a language that has evolved continuously, far beyond its punch-card origins. Modern Fortran standards—1990, 2003, 2008, and beyond—introduce modules, recursion, dynamic memory handling, object-oriented programming, interoperability with C, parallelization features, and clean syntax improvements. The result is a language that’s both familiar and freshly capable. The scientific community didn’t keep Fortran around out of nostalgia; it stayed because it delivers.
In the early stages of this course, we’ll dig into the roots of Fortran to understand why it was created and how its early choices shaped the future of programming languages. But don’t worry—our focus isn’t on turning the course into a history lesson. Instead, we’re going to use that past as a foundation. Understanding why Fortran was built the way it was gives you a deeper appreciation for its elegance and reveals why it still dominates specific domains today.
From there, we’ll gradually expand into the language proper: variables, intrinsic types, expressions, arrays, control flow, and core procedural programming. Fortran’s syntax may appear unusual if your background includes languages like Python or JavaScript, but once you grow accustomed to its style, you’ll discover its clarity and directness. It’s a language designed to express mathematical ideas efficiently, and that mindset shows up in every line of code.
As the articles progress, we’ll explore the parts of Fortran that make numerical programmers smile—multidimensional arrays, intrinsic functions tailored for scientific computing, and the predictable performance that compiled languages offer. You’ll learn why array operations feel natural in Fortran and how the language’s design takes advantage of memory layouts to achieve speed gains without unnecessary complexity.
You’ll also encounter modern Fortran’s more advanced features. Many newcomers don’t realize that you can write modular, type-safe, object-oriented Fortran. Along the way, we’ll walk through modules, user-defined types, operator overloading, and building larger, more maintainable software systems in Fortran. These tools help you move from small scripts to fully structured applications with clarity and confidence.
Parallel computing is another pillar of the language, and it’s an area where the course spends considerable time. High-performance computing isn’t just a niche skill—it’s increasingly part of modern scientific work, machine learning research, energy simulations, and climate forecasting. Fortran embeds parallelism deeply into its design, and by the time you reach the later articles, you’ll be working comfortably with coarrays, OpenMP, MPI, and other approaches to distributed and shared-memory computation. You’ll see how Fortran enables developers to scale programs efficiently across multicore processors and supercomputers, a skillset that remains highly valuable in scientific and industrial applications.
Interoperability is another important theme. While Fortran is powerful on its own, real-world projects often require connecting it with other languages—and modern standards make that surprisingly straightforward. We’ll explore how to interface Fortran with C, call Fortran from Python, and integrate Fortran modules into mixed-language projects. By demystifying these interactions, you’ll gain the flexibility to use Fortran where it shines while still benefiting from the strengths of other languages.
Beyond language mechanics, this course also emphasizes best practices. Fortran projects vary widely in scale—from a small numerical script to multi-million-line climate models built by research teams scattered across the globe. So you’ll learn practical approaches to testing, documentation, code structure, debugging, and project organization. These best practices ensure you’re not just learning to write Fortran, but learning to write robust, maintainable, and future-friendly Fortran.
Throughout these one hundred articles, the goal is to give you a realistic, modern understanding of the language. You’ll see Fortran’s role in scientific computing today, its ecosystem of compilers and tools, and how to approach performance optimization methodically rather than through guesswork. And along the way, you’ll gain an appreciation for the way Fortran blends tradition with innovation.
What makes Fortran compelling is not just speed, or its close relationship with scientific work—it’s the balance it strikes between expressive mathematical clarity and raw computational efficiency. It allows you to write code that feels close to the mathematics behind it, without sacrificing control or performance. In an era where many languages lean heavily into abstraction or convenience, Fortran stands as a reminder that sometimes simplicity and precision are the most powerful tools in the programmer’s toolkit.
If you’re new to the language, you’ll find that learning Fortran feels different from learning something like Rust or JavaScript. It requires a shift in mindset—one that embraces deterministic thinking, clear data structures, careful reasoning about arrays and memory, and a strong connection between your code and the numerical processes it represents. But that shift is incredibly rewarding, especially if you enjoy understanding what’s truly happening under the hood.
By the end of the course, you will have journeyed from the origins of high-level programming to the depths of modern computational science. You’ll understand how Fortran compilers work, how loops and arrays interact with hardware, how to choose the right data structures, and how to make tradeoffs that balance readability with performance. You’ll be able to write programs that scale from a single workstation to a supercomputer and interact seamlessly with other programming environments.
But perhaps most importantly, you’ll gain a perspective on Fortran that’s grounded in its reality rather than outdated stereotypes. You’ll see why scientists continue to trust it, why engineers rely on its reliability, and why researchers appreciate its predictability in complex numerical models. This isn’t a relic of the past; it’s a living, evolving language that has proven itself indispensable across generations of technological change.
So think of this introduction as a doorway. What comes next is a carefully structured journey through a language that’s both timeless and modern. It’s a chance to understand the foundation of much of scientific computing, to strengthen your programming instincts, and to build a skillset that remains relevant no matter what new languages emerge.
Whether you’re here out of curiosity, professional need, academic interest, or a desire to broaden your programming horizons, welcome. You’re stepping into a tradition of computational excellence that spans decades, and by the end of this course, you’ll be able to navigate it with confidence and insight.
Let’s begin.
¶ Fortran
¶ Beginner Topics
1. Introduction to Fortran: History and Evolution
2. Setting Up the Fortran Development Environment
3. Your First Program in Fortran: Hello, World!
4. Understanding the Structure of a Fortran Program
5. Fortran Syntax: Keywords, Operators, and Expressions
6. Variables and Data Types in Fortran
7. Basic Arithmetic Operations in Fortran
8. Using Fortran’s Intrinsic Functions for Basic Calculations
9. Input and Output in Fortran: Reading and Writing Data
10. Understanding and Using Comments in Fortran
11. Introduction to Control Flow: if-else Statements
12. Using Loops in Fortran: do, do while, and do until
13. Writing and Using Simple Functions in Fortran
14. The Importance of Indentation and Readability in Fortran
15. Working with Arrays in Fortran: Declaring and Using
16. Introduction to Strings and Character Arrays in Fortran
17. Using the COMMON Block for Shared Data in Fortran
18. Introduction to Modules and the use Statement
19. Simple Error Handling and Debugging Techniques in Fortran
20. Writing and Using Subroutines in Fortran
¶ Intermediate Topics
21. Working with Multi-Dimensional Arrays in Fortran
22. Introduction to File Handling: Reading and Writing Files
23. Understanding Fortran's Type System and Type Declarations
24. Implementing Function Overloading in Fortran
25. Working with Pointers and Dynamic Memory Allocation
26. Fortran Control Structures: SELECT CASE and IF-THEN-ELSE
27. Introduction to Object-Oriented Features in Fortran
28. Using Derived Types (Structures) in Fortran
29. Writing and Using Interfaces in Fortran
30. Modularizing Code with Fortran Modules
31. Exploring Fortran Intrinsic Functions and Libraries
32. Using Arrays as Arguments in Functions and Subroutines
33. Introduction to String Manipulation in Fortran
34. Recursion in Fortran: Writing Recursive Functions
35. Working with Large Data Sets in Fortran
36. Optimizing Fortran Code for Performance
37. Handling Complex Numbers in Fortran
38. Using the ASSOCIATE and POINTER Constructs in Fortran
39. Understanding Memory Allocation in Fortran: ALLOCATE and DEALLOCATE
40. Error Handling in Fortran: Using STOP and ERROR STOP
41. Introduction to Fortran’s Timing and Performance Tools
42. Using Conditional Compilation in Fortran with Preprocessors
43. Writing Reusable Code in Fortran
44. Working with Dynamic Arrays in Fortran
45. Introduction to Parallel Programming in Fortran
46. Understanding the Fortran Program Execution Flow
47. Building a Simple Command-Line Interface in Fortran
48. Using Fortran to Interface with External Libraries and APIs
49. Debugging Fortran Code Using GDB and Other Tools
50. Writing Fortran Code for High-Performance Computing (HPC)
¶ Advanced Topics
51. Advanced Array Techniques in Fortran: Array Sections and Slicing
52. Implementing Complex Algorithms with Fortran
53. Introduction to Parallel Programming with OpenMP in Fortran
54. Using MPI (Message Passing Interface) for Distributed Computing in Fortran
55. Writing Efficient Numerical Computations in Fortran
56. Using Fortran for Scientific and Engineering Simulations
57. Advanced Memory Management in Fortran
58. Using Fortran for Matrix and Linear Algebra Operations
59. Performance Profiling and Optimization Techniques in Fortran
60. Advanced I/O Techniques in Fortran: Binary and Formatted Files
61. Using External Libraries in Fortran: LAPACK, BLAS, and FFTW
62. Introduction to Fortran’s Object-Oriented Programming Features
63. Using Fortran’s Inheritance and Polymorphism Features
64. Implementing Templates and Generics in Fortran
65. Building Multi-Threaded Applications with OpenMP in Fortran
66. Advanced File I/O Handling with Fortran
67. Fortran and CUDA: GPU Programming for Scientific Applications
68. Writing Fortran Code for Real-Time Applications
69. Integrating Fortran with Python and Other Languages
70. Writing Fortran Libraries and APIs for External Use
71. Working with Big Data in Fortran
72. Interfacing Fortran with Web Technologies (e.g., RESTful APIs)
73. Developing a Fortran-Based High-Performance Computing Cluster
74. Building Scientific Visualization Tools in Fortran
75. Fortran for Geospatial Data Processing and Analysis
76. Working with Fortran and Databases: SQL and NoSQL
77. Building Complex Simulation Frameworks in Fortran
78. Advanced Optimization Techniques: Compiler Options and Pragmas
79. Using Fortran for Statistical Computing
80. Writing and Using Fortran Libraries for Numerical Methods
81. Fortran for Data Science: Machine Learning and Data Mining
82. Building and Using Parallel Libraries in Fortran
83. Advanced Memory Optimization Techniques in Fortran
84. Fortran and Cloud Computing: Scalable Applications in the Cloud
85. Implementing Cryptographic Algorithms in Fortran
86. Building Multi-Platform Fortran Applications
87. Fortran for Financial Modeling and Quantitative Analysis
88. Writing and Managing Large Fortran Projects
89. Using Fortran with WebAssembly for Web-Based Applications
90. Building Custom Fortran Compilers and Interpreters
91. Writing Fortran Code for Parallel File Systems and HPC Clusters
92. Using Fortran for Bioinformatics and Computational Biology
93. Working with Fortran in Embedded Systems and IoT Devices
94. Developing Cross-Language Interfaces with Fortran
95. Building a Scientific Computing Framework in Fortran
96. Performance Tuning for Fortran in Multi-Core Systems
97. Writing Fortran for Multi-Scale and Multi-Physics Simulations
98. Advanced Computational Fluid Dynamics (CFD) with Fortran
99. Integrating Fortran with Machine Learning Libraries
100. The Future of Fortran: Trends, Community, and New Features