5.1.1 Syntax

Header card images  shall consist of a keyword, a value indicator (optional unless a value is present), a value (optional), and a comment (optional). Except where specifically stated otherwise  in this standard, keywords may appear in any order.

A formal syntax, giving a complete definition of the syntax of FITS card images, is given in Appendix A. It is intended as an aid in interpreting the text defining the standard.