Diffsystemer

Diffsystemer is a term used in Swedish computing to describe systems, formats, and methods for identifying and applying differences between data sets. A diff compares two versions of a file or dataset and expresses changes as insertions, deletions, or modifications, often in the form of a patch that can update one version to another without transferring the full content.

Common diff formats include unified diff and context diff, designed for readability by humans and automation by tools. These outputs enable patch programs to apply changes to target files reliably.

Algorithms form the core of diff systems. The Myers diff algorithm computes a shortest edit script to transform one sequence into another, with typical complexity described as O(ND). Real-world tools add optimizations for large files and for handling binary data.

Applications span software development, where diffs drive version control and patch distribution; data synchronization and incremental backups; and database replication, where transmitting differences conserves bandwidth.

Challenges include handling binary data, large repositories, and merge conflicts, as well as ensuring patches apply consistently across different environments and file encodings.

Historically, diff tools originated in Unix-like systems in the late 20th century. The underlying ideas—representing changes as diffs and patches—have shaped modern development workflows and data synchronization approaches.