Software documentation

Software documentation consists of written text or illustrations that accompany computer software. It can be embedded directly within the source code or exist as separate files. This documentation serves to explain how software operates or how to use it. Because different people have different roles, documentation can mean different things to different users. It is a vital component of the software engineering process. Without it, managing complex systems becomes much more difficult.

The process often begins with requirements documentation. This is a description of what a software system must do or its specific qualities. It acts as a foundation or an agreement for what will be implemented. Requirements are used by many people, including customers, project managers, and developers. They can be written in natural language, drawn as figures, or expressed as mathematical formulas. Sometimes requirements are implicit and hard to uncover. If requirements are missing, software changes become more expensive and error-prone. The level of detail needed often depends on the software's complexity or its life expectancy.

Architecture or design documentation provides a high-level overview of the software. These documents are often described as a third derivative from the code. They do not explain how to program a specific routine. Instead, they list the general requirements that motivate a routine's existence. A good architecture document focuses more on explanation than on tiny details. Another design tool is the trade study, often presented as a whitepaper. A trade study examines one specific aspect of a system. It describes different alternatives and lists the pros and cons of each. This should be an impartial, scientific endeavor rather than a marketing tool.

In enterprise development, the Database Design Document (DDD) is very important. This document contains conceptual, logical, and physical design elements. It creates a common source of information for database designers, developers, and administrators. For relational database systems, the DDD must include an Entity-Relationship Schema. This schema defines entity sets, their attributes, and their relationships. It also includes details like candidate keys and constraints. It is vital to update these documents whenever any change occurs in the database. This ensures all actors in the development scene have accurate information.

Technical documentation often focuses on the code itself. This includes README files and Application Programming Interface (API) documentation. Technical notes are used by developers, testers, and sometimes end-users. In high-end fields like aerospace or medical equipment, this documentation is critical. Good code documentation can actually reduce the costs of maintaining software. Many programmers use a reference guide style to look up functions quickly. Some tools, such as Javadoc or Doxygen, can auto-generate this documentation. These tools extract comments from the source code to create HTML or text files. This makes it easier to keep the documentation up to date.

Some computer scientists advocate for new ways to handle documentation. Donald Knuth suggested literate programming (LP). In LP, documentation is written at the same time and place as the source code. While languages like Haskell have some support for this, it is not widely used. Another approach is the "Docs as Code" method. There is also elucidative programming, which is a practical application of literate programming. This paradigm suggests that source code and documentation should be stored separately. This helps developers access information during activities like code walks or porting software.

Finally, user documentation is designed specifically for the person using the program. Unlike code documents, these describe how to use the features of an application. User documentation is often seen as a contract specifying what the software will do. It must be consistent, simple, and include a thorough index. There are three main ways to organize this information. A tutorial approach guides new users through tasks step by step. A thematic approach organizes chapters by specific areas of interest. These guides help users realize the full potential of the software they are using.