Meaning: This quote by John Carmack, a renowned computer programmer and co-founder of id Software, delves into the complexities and considerations involved in adding new features to a software system. In essence, Carmack is highlighting the multifaceted nature of the cost associated with adding a feature, emphasizing that it encompasses more than just the time and effort required to write the code. Instead, he suggests that the cost also encompasses the potential hindrance to future expansion that might arise from the addition of a new feature. Furthermore, Carmack advises that the selection of features should be strategic, aiming to avoid conflicts and ensure that they complement each other rather than create obstacles.

When considering the cost of adding a feature, it's important to recognize that the implications extend beyond the immediate development phase. While the initial investment of time and resources in coding the feature is a significant component, Carmack's insight draws attention to the longer-term consequences. The concept of an "obstacle to future expansion" underscores the idea that adding a feature can potentially introduce complexities or constraints that may impede the seamless integration of additional features or the scalability of the system. This aligns with the broader principles of software architecture and design, where decisions made at one stage can have far-reaching effects on the system's ability to evolve and adapt over time.

Carmack's reference to features "fighting each other" speaks to the potential conflicts and complications that can arise when multiple features are introduced to a system. In the context of software development, these conflicts can manifest in various ways, such as incompatible functionalities, performance bottlenecks, or increased maintenance overhead. By cautioning against the selection of features that are at odds with each other, Carmack emphasizes the importance of coherence and synergy in feature development. This aligns with the concept of architectural integrity, where the overall structure of a system should support the cohesive integration of its individual components.

In practical terms, this quote underscores the need for careful consideration and prioritization when it comes to feature selection and implementation. It prompts software developers and decision-makers to weigh the short-term benefits of a particular feature against its potential long-term impacts on the system's flexibility and extensibility. Furthermore, it emphasizes the value of taking a holistic view of the software architecture, ensuring that new features align with the overarching design principles and contribute to the system's overall coherence.

From a strategic perspective, Carmack's insight encourages a proactive approach to feature management, where the emphasis is not only on adding new capabilities but also on cultivating a harmonious and sustainable ecosystem of features. This involves evaluating the interplay between different features and assessing how they collectively contribute to the system's functionality and adaptability. By doing so, software teams can mitigate the risk of feature bloat, technical debt, and architectural fragility, thereby fostering a more resilient and evolvable software landscape.

In conclusion, John Carmack's quote encapsulates essential considerations for software development, highlighting the multifaceted nature of the cost of adding a feature. It serves as a reminder that the implications of feature addition extend beyond the immediate coding effort, encompassing the potential impact on future expansion and the need for strategic feature selection. By embracing this perspective, software practitioners can make informed decisions that not only address immediate requirements but also contribute to the long-term health and sustainability of the systems they build.