Indent style

In computer programming, an indent style is a convention governing the indentation of blocks of code to convey the program's structure. This article largely addresses the C programming language and its descendants, but can be (and frequently is) applied to most other programming languages (especially those in the curly bracket family). Indent style is just one aspect of programming style.

Indentation is not a requirement of most programming languages. Rather, programmers indent to better convey the structure of their program to human readers. In particular, indentation is used to show the relationship between control flow constructs such as conditions or loops and code contained within and outside them. However, some programming languages (such as Python and Occam) use the indentation to determine the structure instead of using braces or keywords.

The size of the indent is usually independent of the style. Many early programs used tab characters for indentation, for simplicity and to save on source file size. Unix editors generally view tabs as equivalent to eight characters, while Macintosh environments would set them to four, creating confusion when code was transferred back and forth. Modern programming editors are now often able to set arbitrary indentation sizes, and will insert the appropriate combination of spaces and tabs. They can also help with the cross-platform tab confusion by being configured to insert only spaces.

There are a number of computer programs that automatically correct indent styles as well as the length of tabs. A famous one among them is indent, a program included with many Unix-like operating systems. These programs work best for those who use an indent style close to that considered "proper" by their programmers; those who use other styles will more likely become frustrated.