Semantic Versioning: A Three-Part Numbering System
Semantic Versioning (SemVer) is a widely used convention for assigning software versions. It uses a three-part Major.Minor.Patch number to create unique identifiers for software states.
Why it exists
Software development requires a way to assign unique identifiers to unique states of the software. Without a shared convention, this process can be chaotic, using inconsistent numbers, dates, or letters that make it difficult to track changes or manage dependencies between different software components.
The mental model
Think of Semantic Versioning (SemVer) as a universal language for software versions. It replaces arbitrary naming with a predictable, three-part number (Major.Minor.Patch) that provides a formal structure for both humans and machines to understand.
How it works
The core of SemVer is a three-part version number. For example, in 2.5.1, 2 is the Major version, 5 is the Minor version, and 1 is the Patch version. SemVer also allows for optional tags. A hyphen indicates a prerelease tag (e.g., 1.0.0-alpha), while a plus sign indicates build metadata (e.g., 1.0.0+build.456). Some implementations may even add a fourth number to denote a specific build.
When to use it
Use SemVer when you need a clear, widely understood scheme for labeling software releases. It is the most common system and provides a consistent foundation for managing software states and dependencies.
When not to use it
SemVer is not the only option. Some projects use calendar versioning (CalVer), where the version is based on the release date (e.g., 2024.05.10), which is common for products with time-based release schedules. Other historical systems used letters and other characters, which is now less common but demonstrates that not all versioning is semantic.
One canonical example
While SemVer is a three-part system, it can be extended. Adobe Flash, for instance, was known for using a four-part version number, with the fourth number denoting the software build.
Interview question
What is the fundamental structure of a Semantic Versioning number?
- a.A three-part number: Major.Minor.Patch.Correct
- b.A date-based system like YYYY.MM.DD.
- c.A flexible system using letters, numbers, or dates.
- d.A four-part number including a build identifier.
Why? this is the answer
The card explicitly states that the core of Semantic Versioning is a three-part Major.Minor.Patch number. While some implementations may extend it to four parts, this is not its fundamental structure.
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