Indent Style - K&R Style

K&R Style

The K&R style, so named because it was used in Kernighan and Ritchie's book The C Programming Language, is commonly used in C. It is also used for C++, C#, and others.

When adhering to K&R, each function has its opening brace at the next line on the same indentation level as its header, the statements within the braces are indented, and the closing brace at the end is on the same indentation level as the header of the function at a line of its own. The blocks inside a function, however, have their opening braces at the same line as their respective control statements; closing braces remain in a line of their own, unless followed by an else or while keyword.

In this style a control statement with only a single statement in its scope may omit the braces. The C Programming Language refers to this as fertile soil for bugs (programming logical errors) and discourages it.

int main(int argc, char *argv) { ... while (x == y) { something; somethingelse; if (some_error) { /* the curly braces around this code block could be omitted */ do_correct; } else continue_as_usual; } finalthing; ... }

In old versions of the C programming language, the functions, however, were braced distinctly. The opening function brace of a function was placed on the line following after the declaration section and at the same indentation level as the declaration (header of the function). This is because in the original C language, argument types needed to be declared on the subsequent line (i. e., just after the header of the function), whereas when no arguments were necessary, the opening brace would not appear in the same line with the function declaration. The opening brace for function declarations was an exception to the currently basic rule stating that the statements and blocks of a function are all enclosed in the function braces.

/* Original pre-ISO C style without function prototypes */ int main(argc, argv) int argc; char *argv; { ... }