Notation
The barre is often signed on tablature as "C" with the fret number as Roman numeral, such as
CVII CVIII CXII CII E--------7--------8--------13-------2------- B--------9--------8--------15-------4------- G--------9--------8--------14-------2------- D--------9--------10-------12-------4------- A--------7--------10-------12-------2------- E--------7--------8--------12-------2------- E Cm Dm B7In some notation styles (particularly classical staff notation), the "C" is usually omitted, with the number of courses to be barred (from the highest-tuned downwards) written as an index (superscript). For example: on a guitar, VII4 indicates a barre on the 7th fret over the highest four strings (D, G, B, and E). There is no rule for whether full barre chords are written with indices (e.g. "6" for a standard guitar) or without; it is a matter of personal taste for the editor. It is customary to place the barre sign above the staff, with a spanning line to mark duration.
Read more about this topic: Barre Chord