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Subroutines

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May 1, 2024 Updated June 2, 2025 24 minute read

An Introduction to Subroutines: Building Blocks of Modern Programming

Subroutines, in their most fundamental sense, are named, self-contained blocks of code designed to perform a specific task. Imagine you are writing a complex set of instructions; if you find yourself writing the same sequence of steps repeatedly, you could instead define that sequence once, give it a name, and then simply call that name whenever you need those steps performed. This is the core idea behind subroutines. They are a cornerstone of efficient and organized programming, allowing developers to write cleaner, more manageable, and more reliable software.

Working with subroutines brings several engaging aspects to the world of programming. Firstly, they introduce a level of abstraction, allowing programmers to think about problems at a higher level without getting bogged down in the minutiae of every single instruction. Secondly, the modularity offered by subroutines greatly enhances collaboration; different team members can work on different subroutines independently, knowing that their pieces will fit together to form a functional whole. Finally, mastering subroutine design is a key step towards writing sophisticated applications, as they form the basis for more complex structures like libraries, frameworks, and Application Programming Interfaces (APIs).

Introduction to Subroutines

For those new to programming, or perhaps exploring it out of curiosity, the concept of a subroutine might seem abstract. However, it's a beautifully simple idea that mirrors many real-world scenarios. Understanding subroutines is a foundational step in learning almost any programming language and is crucial for developing good coding habits from the start.

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Reading list

We've selected 35 books that we think will supplement your learning. Use these to develop background knowledge, enrich your coursework, and gain a deeper understanding of the topics covered in Subroutines.
Provides a deep dive into computer systems, covering topics such as processor architecture, memory management, and operating systems. It includes a chapter on subroutines that discusses their implementation and optimization.
This comprehensive book on Java concurrency covers topics such as thread pools and synchronization primitives, which are essential for understanding the implementation and use of subroutines in Java.
Bridges the gap between high-level programming and the underlying hardware. It provides detailed explanations of how procedures (subroutines) are implemented, including stack organization, calling conventions, and the relationship between source code and machine code. It must-read for gaining a deep understanding of how subroutine calls work at a fundamental level and is commonly used as a textbook.
Must-read for learning how to write readable, maintainable, and well-structured code. It dedicates significant attention to writing clean functions (subroutines), emphasizing principles like small size, doing one thing, and meaningful names. It is highly practical and directly applicable to improving the quality of code involving subroutines.
Comprehensive guide to software construction, with excellent chapters dedicated to the art and science of creating high-quality routines (subroutines, functions, procedures). It provides practical advice on designing, implementing, and testing subroutines for clarity, correctness, and performance. It is highly valuable as a reference tool and is considered a must-read for developers seeking to solidify their understanding of fundamental programming practices.
This classic book provides a comprehensive guide to software development, covering topics such as design, testing, and maintenance. It includes a chapter on subroutines that provides valuable insights into their use and implementation.
This official guide to the Rust programming language covers topics such as memory safety and concurrency, which are relevant to the design and implementation of subroutines.
Introduces the Go programming language, which supports lightweight subroutines known as goroutines. It provides a practical guide to writing concurrent and scalable code.
Introduces concurrency in C++, covering topics such as thread safety, synchronization, and data parallelism. It provides practical examples of using subroutines in multithreaded C++ applications.
Offers timeless advice on becoming a better software developer. It advocates for building flexible and maintainable systems, which involves effective use of modularity and well-designed components, including subroutines. It provides valuable insights into writing code that is easy to understand and modify. This must-read for developers at all levels.
Provides a comprehensive overview of subroutine libraries, covering their design, implementation, and use. It is particularly relevant for those interested in developing and maintaining large-scale software systems.
Introduces functional programming concepts in Scala, including the use of subroutines as first-class functions. It is suitable for programmers with some experience in object-oriented programming.
Teaches programming language concepts by guiding the reader through the implementation of interpreters for various language features. It provides a deep understanding of how constructs like procedures, scope, closures, and evaluation strategies work from an implementation perspective. It valuable textbook for advanced undergraduate or graduate students studying programming languages.
A widely used textbook for operating systems courses, this book explains fundamental concepts including processes, threads, and memory management. It provides crucial context on how the operating system manages the execution of code, including the role of the process stack and context switching, which are intrinsically linked to subroutine calls. It useful reference and common textbook in undergraduate and graduate programs.
Provides a catalog of techniques for improving the internal structure of existing code without changing its external behavior. Many refactoring techniques directly involve functions and methods, such as extracting methods, consolidating conditional expressions, and composing methods. It is highly relevant for understanding how to improve the design and clarity of subroutines in practical settings.
This accessible book introduces design patterns, including creational patterns that utilize subroutines. It is an excellent choice for beginners looking to gain a practical understanding of this topic.
Another prominent textbook on operating systems, this book offers a comprehensive overview of OS principles and implementations. It covers processes, memory management, and the kernel's role in managing program execution, providing a solid foundation for understanding the environment in which subroutines run. It valuable reference and often used as a textbook in computer science programs.
Offers a detailed exploration of assembly language programming on x86 processors. It is highly relevant for understanding how subroutines are implemented at the machine level, covering topics like calling conventions, stack frames, and parameter passing. It serves as a valuable reference for those wanting to deepen their understanding of the low-level details often abstracted away by high-level languages.
This classic book introduces fundamental design patterns in object-oriented programming. Many of these patterns describe established ways to structure interactions between objects using methods (which are a form of subroutine). Understanding these patterns deepens one's understanding of how subroutines can be used effectively in larger software designs. It key reference for software architecture and design.
The first volume of Knuth's monumental series lays the groundwork for computer programming. It includes detailed discussions on fundamental algorithms and data structures, and analyzes the efficiency of basic operations, including subroutine linkages. While mathematically rigorous and challenging, it offers a deep, classic perspective on the underlying principles of computation and program execution.
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