RCS--A System for Version Control

Walter F. Tichy

Department of Computer Sciences
Purdue University
West Lafayette, Indiana 47907

ABSTRACT

An important problem in program development and maintenance is version control, i.e., the task of keeping a software system consisting of many versions and configurations well organized. The Revision Control System (RCS) is a software tool that assists with that task. RCS manages revisions of text documents, in particular source programs, documentation, and test data. It automates the storing, retrieval, logging and identification of revisions, and it provides selection mechanisms for composing configurations. This paper introduces basic version control concepts and discusses the practice of version control using RCS. For conserving space, RCS stores deltas, i.e., differences between successive revisions. Several delta storage methods are discussed. Usage statistics show that RCS's delta storage method is space and time efficient. The paper concludes with a detailed survey of version control tools.

Keywords: configuration management, history management, version control, revisions, deltas.

Table of Contents

• 1. Introduction
• 2. Getting started with RCS
  • 2.1. Automatic Identification
• 3. The RCS Revision Tree
  • 3.1. When are branches needed?
  • 3.2. Revisions are represented as deltas
• 4. Locking: A Controversial Issue
• 5. Configuration Management
  • 5.1. RCS Selection Functions
  • 5.2. Combining MAKE and RCS
• 6. Usage Statistics
• 7. Survey of Version Control Tools
• Footnotes