Ĭomments are sometimes used to document contracts in the design by contract approach to programming.ĭepending on the intended audience of the code and other considerations, the level of detail and description may vary considerably.įor example, the following Java comment would be suitable in an introductory text designed to teach beginning programming: In between these views is the assertion that comments are neither beneficial nor harmful by themselves, and what matters is that they are correct and kept in sync with the source code, and omitted if they are superfluous, excessive, difficult to maintain or otherwise unhelpful. Others suggest code should be extensively commented (it is not uncommon for over 50% of the non- whitespace characters in source code to be contained within comments). Some assert that source code should be written with few comments, on the basis that the source code should be self-explanatory or self-documenting. Need for comments Įxperts have varying viewpoints on whether, and when, comments are appropriate in source code. Some of these are informal and based on personal preference, while others are published or promulgated as formal guidelines for a particular community. There are various normative views and long-standing opinions regarding the proper use of comments in source code. The occurrence of this phenomenon can be easily seen from online resources that track profanity in source code. Sometimes programmers will add comments as a way to relieve stress by commenting about development tools, competitors, employers, working conditions, or the quality of the code itself. # vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4 For example, the "modeline" feature of Vim which would change its handling of tabs while editing a source with this comment included near the top of the file: Many editors and IDEs will read specially formatted comments. Inserting such a /* Fall thru */ comment for human readers was already a common convention, but in 2017 the gcc compiler began looking for these (or other indications of deliberate intent), and, if not found, emitting: "warning: this statement may fall through". * loop backwards through all elements returned by the server (they should be processed chronologically)*/ for ( i = ( numElementsReturned - 1 ) i >= 0 i - ) In this case it should explain the logic behind the code rather than the code itself. Planning and reviewing Ĭomments can be used as a form of pseudocode to outline intention prior to writing the actual code. There are many different ways of writing comments and many commentators offer conflicting advice. How best to make use of comments is subject to dispute different commentators have offered varied and sometimes opposing viewpoints. For example, Ada comments are line comments: they start with - and continue to the end of the line. Other languages support only one type of comment. For example, C++ has block comments delimited by /* and */ that can span multiple lines and line comments delimited by //. Some programming languages employ both block and line comments with different comment delimiters. Line comments either start with a comment delimiter and continue until the end of the line, or in some cases, start at a specific column (character line offset) in the source code, and continue until the end of the line. Some programming languages (such as MATLAB) allow block comments to be recursively nested inside one another, but others (such as Java) do not. This region is specified with a start delimiter and an end delimiter. īlock comments delimit a region of source code which may span multiple lines or a part of a single line. The flexibility provided by comments allows for a wide degree of variability, but formal conventions for their use are commonly part of programming style guides.Ĭomments are generally formatted as either block comments (also called prologue comments or stream comments) or line comments (also called inline comments). The syntax of comments in various programming languages varies considerably.Ĭomments are sometimes also processed in various ways to generate documentation external to the source code itself by documentation generators, or used for integration with source code management systems and other kinds of external programming tools. They are added with the purpose of making the source code easier for humans to understand, and are generally ignored by compilers and interpreters. In computer programming, a comment is a programmer-readable explanation or annotation in the source code of a computer program. An illustration of Java source code with prologue comments indicated in red and inline comments in green. For comments in Wikipedia markup, see Help:Wiki markup#Character formatting and WP:COMMENT.
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