; a comment

[sectiona]
key1=value1 ; another comment
key2=value2

[sectionb]
keyb1=valueb1
keyb2=valueb2

• Semicolon on the beginning of a line means the rest of the line is a comment. It logically belongs to the line following, not the proceeding one. Normally you don’t add comments to the tail ends of values; you put them on a line by themselves. However a ; not inside quotes will mark the start of such a comment.
• [Sections] are unique. Section names contain punctuation or spaces.
• Keys are unique within sections. They can contain punctuation, anything but space and =.
• The value may be quote enclosed. The value may contain spaces, even without being enclosed in quotes. It may be empty.
• Everything is case sensitive. Leading and trailing blanks are not significant.
• There is usually a blank line between sections.
• The *.ini file might be encoded with ASCII, UTF-8 or UTF-16, big or little-endian. The encoding is not internally marked, other than perhaps by a warning comment.
• The order of sections and the order of keys within sections is not significant, though it is convenient to order the sections and keys alphabetically.
• Some key=value pairs may occur outside section, at the top before the first [section] marker.