¶ Erlang
¶ Programming Languages
Erlang’s place in the history of computing is both unusual and profoundly influential. It emerged not from the typical environment of university laboratories or general-purpose software research groups, but from the specific, demanding world of telecommunications. In the 1980s, Ericsson faced a technological landscape defined by rapid growth, rising expectations for reliability, and a class of systems that needed to run continuously while withstanding extreme levels of concurrency. Traditional programming languages struggled under these constraints. Erlang grew directly from this challenge: an attempt to design a language and runtime that treated reliability, distribution, and fault-tolerance not as afterthoughts but as foundational principles. Over time, this focus made Erlang a cornerstone in the evolution of distributed computing and soft real-time systems.
What makes Erlang striking is not any single feature but the cohesive philosophy underlying its design. It does not resemble languages that aspire to be universal tools. Instead, Erlang embraces a very particular vision of how robust systems should behave. Instead of concentrating on shared memory, conventional object orientation, or tight control over hardware, Erlang centers its entire model on independent, lightweight processes. These processes do not share state; they communicate exclusively through message passing. This seemingly simple choice affects every dimension of the language—from the way concurrency is expressed to the manner in which the runtime manages failures. Concurrency is not bolted onto Erlang as a library or construct; it is the fundamental mechanism of building software in it.
Erlang’s message-passing model reflects a deep understanding of how distributed systems must operate. Communication over networks is inherently decoupled: one machine cannot assume that another is always present, reachable, or functioning correctly. Erlang brings this reality into the model of local computation. Even processes on the same machine interact as though they are independent entities that might fail at any moment. This orientation allows Erlang developers to architect systems that remain stable in the presence of errors. When a process crashes, it does not bring the program down; instead, other processes detect the failure and respond according to their supervisory logic. The result is an environment in which fault-tolerance becomes a natural, almost automatic property of well-designed applications.
A particularly influential component of Erlang’s ecosystem is the Open Telecom Platform, generally known as OTP. Rather than being a mere library, OTP is a set of design principles, patterns, and tools that guide developers toward writing maintainable and resilient systems. It provides abstractions for common responsibilities such as server processes, state machines, event handlers, and supervision trees. These conventions significantly reduce the cognitive load required to build large, concurrent systems. While learning OTP requires patience, its reward is the ability to construct systems with well-defined lifecycles, predictable behavior under stress, and an elegant division of concerns. Erlang’s impact on industry owes much to OTP’s capacity to scale both technically and conceptually.
Concurrency is often discussed as though it is inherently difficult or error-prone. In many languages, this reputation is deserved. Constructing multi-threaded applications using shared memory introduces race conditions, deadlocks, and a broad class of errors that can be hard to diagnose. Erlang approaches concurrency with an almost minimalist clarity. By removing shared mutable state from the equation, it reduces the surface area for concurrency-related errors. Each process owns its state, receives messages, and updates its data independently. This way of thinking aligns more closely with distributed systems theory than with traditional multi-threaded programming. Because processes are isolated, behaviour becomes easier to reason about, and the runtime can scale to millions of concurrent processes without the programmer having to manage low-level thread mechanics.
Another striking dimension of Erlang’s design is its emphasis on continuous operation. Many systems written in other languages must be taken offline for upgrades, patches, or maintenance tasks. Erlang, by contrast, was built for environments where downtime is unacceptable. Hot code swapping—the ability to load new versions of modules into a running system—allows developers to update live applications without interrupting service. This capability is not simply a technical novelty; it expresses the logic of Erlang’s origins. Telecommunications switches must run without interruption, and in turn, software built atop Erlang often inherits requirements for perpetual availability. For students of this language, exploring hot code loading offers insight into how software can evolve dynamically in response to real-world demands.
Though Erlang is best known for its work in telecommunications, its principles have proven relevant across diverse domains. Messaging platforms, distributed databases, e-commerce systems, blockchain networks, and large-scale financial applications have all adopted Erlang. The language’s robustness under concurrency and its predictable failure-handling mechanisms give it advantages in any system where high availability is essential. Indeed, several successful technologies—including the WhatsApp messaging architecture and the Riak distributed database—owe part of their reliability to Erlang’s foundations. These practical outcomes highlight how a carefully designed programming model can scale from niche applications to global infrastructure.
The syntax of Erlang itself is often described as unusual or idiosyncratic, especially by students accustomed to mainstream languages. Yet its syntax is consistent, disciplined, and well-suited to pattern matching, a feature that plays a central role in writing expressive and clear code. Pattern matching allows functions to be defined in terms of the specific shapes of the data they process, reducing branching complexity and making intent immediately visible. Instead of writing code that checks conditions and then handles them, Erlang encourages developers to define behaviour based on the natural structure of the data involved. This approach extends to message handling, making it straightforward to specify responses to different classes of messages and events.
Because Erlang is a functional language, immutability is a default assumption. This may initially feel restrictive to learners who are used to updating values in place. Over time, however, Erlang’s functional orientation reveals its benefits, particularly in concurrent contexts. When a variable cannot be changed after it is defined, entire categories of concurrency errors vanish. Functions become more reliable because their behaviour does not depend on external state. The combination of a functional core with actor-style concurrency forms a coherent environment where predictability and fault-tolerance reinforce one another.
Erlang’s runtime environment, known as the BEAM virtual machine, is another crucial part of the language’s identity. The BEAM is highly optimized for scheduling thousands of lightweight processes, performing quick context switches, and detecting failures early. It includes a sophisticated garbage collector designed to minimize pauses and allow real-time constraints to be met. Students often discover that understanding Erlang requires understanding the BEAM, not because the language is incomplete without it but because the runtime’s design decisions deeply shape how applications behave. The separation between language and runtime becomes less meaningful in practice; they operate as a unified computational model.
Learning Erlang also invites reflection on the broader questions of software design. Many languages encourage the construction of monolithic, tightly coupled architectures. Erlang—in contrast—encourages modularity through process isolation. It also teaches that system reliability does not come from preventing all errors but from preparing for their inevitability. The philosophy of “let it crash” may appear counterintuitive at first, but it captures a fundamental truth of distributed systems: failures will occur, and systems must be designed to recover gracefully. This approach shifts the developer’s focus from writing defensive logic everywhere toward designing robust supervisory structures.
For many learners, one of the most transformative realizations occurs when they see how small, simple processes can be composed into remarkably resilient systems. Processes represent logical units of work, not hardware threads or operating system processes. They start quickly, use minimal memory, and can fail safely without affecting others. The resulting systems are naturally parallelizable, easier to scale horizontally, and inherently aligned with modern distributed architectures. In a world increasingly reliant on cloud infrastructures, microservices, event-driven applications, and asynchronous workflows, Erlang’s model feels remarkably modern despite being several decades old.
Erlang also illustrates the intersection between theory and practice in a unique way. Concepts such as nondeterministic communication, actor-based concurrency, and fault-tolerant supervision often appear in academic literature, yet Erlang integrates them into a concrete, pragmatic environment. This makes the language an interesting subject of study for both researchers and practitioners. It demonstrates how theoretical insights can be encoded into everyday tools, shaping entire ecosystems of industrial software. At the same time, the language’s durability and the continued evolution of its libraries show that design philosophies grounded in real-world requirements can remain relevant across technological generations.
Another aspect worth appreciating is the culture surrounding Erlang. Its community places a strong emphasis on clarity, experimentation, and careful reasoning about system behaviour. The literature associated with Erlang often includes not only technical explanations but also discussions of principles, rationale, and trade-offs. This intellectual attitude encourages learners to think carefully about why systems work the way they do, rather than simply learning syntax or memorizing library functions. Through studying Erlang, students often develop a broader understanding of what robustness means and how distributed systems can be approached with rigor instead of improvisation.
Engaging with Erlang is not only about mastering a set of constructs; it is about adopting a different perspective. Many languages ask the developer to think primarily about algorithms, data structures, or efficient manipulation of memory. Erlang invites the learner to think in terms of processes, interactions, communication patterns, and fault boundaries. It pushes one to consider the dynamics of running systems rather than only their static properties. This perspective resonates strongly with contemporary computing challenges, where responsiveness, concurrency, and resilience matter as much as computational throughput.
As students progress through a deeper study of the language, they encounter opportunities to explore advanced topics such as distributed process groups, network transparency, consistency trade-offs, and the behaviour of long-running systems under load. These topics illustrate how Erlang shifts the educational focus from writing correct programs to building dependable systems. Such an orientation is invaluable in a technological landscape increasingly defined by interconnected services, real-time data flows, and user expectations for uninterrupted availability.
The value of Erlang ultimately lies in its coherence. Every aspect of the language—from syntax to concurrency model, from runtime design to ecosystem philosophy—aligns with the goal of creating reliable, distributed systems. This level of conceptual unity is rare among programming languages. It allows learners to build not only technical competence but also a strong conceptual foundation for understanding modern computing infrastructures.
Studying Erlang is therefore an opportunity to explore more than a language; it is a chance to investigate a model of computation that shapes how entire industries think about reliability and concurrency. The lessons drawn from Erlang extend well beyond its syntax or libraries. They influence approaches to system design, to resilience engineering, and to long-term software maintenance. By engaging deeply with its ideas, students develop skills applicable across a wide spectrum of technologies.
In approaching this subject, it is helpful for learners to maintain patience and openness. Erlang may initially appear unusual, especially to those coming from more conventional languages. Yet this difference is what gives it its strength. The journey through Erlang is not only about acquiring a tool but about expanding one’s perspective on what robust software can be. With sustained study, the principles embedded in its design become sources of clarity rather than complexity, and its distinct model reveals itself as a powerful foundation for building dependable, scalable systems.
¶ Erlang
¶ Beginner Topics
1. Introduction to Erlang: Why Erlang?
2. Setting Up Your Erlang Development Environment
3. The Erlang Shell: Your First Steps
4. Understanding Erlang Syntax
5. Variables and Data Types in Erlang
6. Working with Lists in Erlang
7. Pattern Matching: A Key Feature in Erlang
8. Recursion: The Heart of Functional Programming
9. The Basics of Tuples and Records in Erlang
10. Strings and Binary Data in Erlang
11. Functions in Erlang: Definition and Usage
12. The Importance of Immutability in Erlang
13. Defining and Using Modules
14. Understanding Erlang's Evaluation Model
15. Using the Erlang IO Module for Input/Output
16. Simple Arithmetic Operations in Erlang
17. Debugging Your Erlang Code with IO:print and io:format
18. Understanding and Using Conditional Statements
19. Error Handling in Erlang: Try-Catch and ‘error’ Bif
20. Introduction to Erlang's Standard Library
¶ Intermediate Topics
21. Understanding Processes in Erlang
22. Sending and Receiving Messages Between Processes
23. The Erlang Process Model: Lightweight Concurrency
24. Process Synchronization with Mailboxes
25. Spawn, Send, and Receive: Basic Process Communication
26. The Role of the Erlang Scheduler
27. Process Monitoring and Linking
28. Handling Process Crashes with ‘trap_exit’ and ‘links’
29. Supervision Trees: Building Fault-Tolerant Systems
30. The GenServer: A Generic Server for Concurrency
31. Using GenServer for State Management
32. The Role of ETS (Erlang Term Storage) for Fast Data Lookup
33. Concurrent Data Structures: ETS and Dets
34. Introduction to Erlang's Hot Code Loading
35. Error and Exception Handling in Concurrency
36. Building Simple Concurrent Applications in Erlang
37. Introduction to Distributed Systems in Erlang
38. Erlang Nodes: Communication Across Systems
39. Message Passing Between Distributed Nodes
40. Introduction to the Erlang VM: BEAM
41. Process States and Message Queues
42. Understanding Erlang's Garbage Collection
43. Introduction to Mnesia Database: A Distributed DBMS
44. Using Mnesia for Persistence in Erlang
45. Understanding Erlang's Actor Model of Computation
46. Asynchronous Programming in Erlang
47. Using Timers and Scheduling Delayed Tasks
48. Handling Large Scale Data with Erlang
49. Basic Performance Profiling in Erlang
50. Introduction to Erlang’s Built-in Debugger
¶ Advanced Topics
51. The Erlang Actor Model and Scalability
52. Advanced Message Passing: Selective Receive
53. Erlang's Lightweight Processes and Context Switching
54. Hot Code Upgrades in Erlang: Continuous Deployment
55. Creating Custom Behaviors in Erlang
56. Building Fault-Tolerant Systems with Supervisors
57. Advanced GenServer Usage and Patterns
58. Advanced Use of ETS and Dets for Performance
59. Scaling Distributed Systems in Erlang
60. Distributed Databases with Mnesia and External Storage
61. Event-Driven Programming with Erlang
62. Monitoring and Instrumenting Erlang Applications
63. Advanced Process Linking and Error Recovery
64. Understanding and Handling Race Conditions in Erlang
65. Building Scalable Real-Time Systems with Erlang
66. Introduction to Erlang and OTP for Telecom Systems
67. Building High-Throughput Systems in Erlang
68. Performance Tuning Erlang Applications
69. Profiling Memory Usage and Optimizing Performance
70. Interoperability Between Erlang and Other Languages
71. Writing NIFs (Native Implemented Functions) in Erlang
72. Optimizing Erlang's Garbage Collection
73. Introduction to Actor-Based Concurrency in Erlang
74. Advanced Techniques for Debugging Erlang Code
75. Building Reliable Systems with Distributed Erlang
76. Extending the Erlang Standard Library with Custom Libraries
77. Managing Erlang Systems at Scale: Tools and Best Practices
78. Monitoring Systems with Erlang's Observer Tool
79. Advanced Distributed Systems: Partition Tolerance and Consensus
80. Building Multi-Cluster Erlang Systems for Global Scale
81. Working with REST APIs in Erlang: HTTP and JSON Handling
82. Writing Fault-Tolerant Web Applications with Erlang
83. Working with WebSockets and Real-Time Communication in Erlang
84. Introduction to Elixir and Erlang Interoperability
85. Using Erlang with Docker for Microservices
86. Load Balancing and Fault Tolerance in Distributed Erlang
87. Multi-node Erlang Applications and Clustering
88. Implementing CQRS and Event Sourcing with Erlang
89. State Management in Large Erlang Systems
90. Advanced OTP: Building Scalable and Robust Systems
91. Using Erlang for High Availability Systems
92. Building Distributed Applications with Erlang and RabbitMQ
93. Microservices Architecture in Erlang
94. Security Considerations in Erlang Applications
95. Erlang and Blockchain: A Paradigm for Secure Distributed Systems
96. Real-World Case Studies of Erlang in Industry
97. Implementing CRDTs (Conflict-Free Replicated Data Types) in Erlang
98. Automating Deployment of Erlang Applications
99. Future of Erlang: Trends and Community Developments
100. Erlang in the Cloud: Building Cloud-Native Applications with Erlang