Tabs and only tabs should be used for indenting. Each level of indent should be exactly one tab.

For vi/vim users who dislike the amount of space taken up by tabs the following mode line should be inserted in a comment in the first or last 5 lines of the file:

vi:set ai sw=2 ts=2 noexpandtab:

Given that modern editors are no longer limited to 80 character widths, line lengths are less important, however readability is important. Lines longer than 75 characters should be considered for breaking. Lines longer than 100 characters must be broken.

Line breaks should be at an operator, and the following line should be indented.