Layout of input

Empty records and leading blanks in records are allowed and ignored, and can be used to enhance clarity and readability of the input file for human readers.

An exclamation mark (!) is interpreted by the input reading routine as denoting the end-of-line. Instead of the exclamation mark you may also use a double colon (::). The part of the line after the exclamation mark (double colon) - including the ! or :: itself - is ignored. In this way one can include comments and clarifying remarks, which will not be echoed in the output header (compare the key COMMENT).