A dot placed after a note increases the time
value of the note by a half. A half-note (minim), normally worth two beats
(in 4/4 time), when written with a dot becomes worth three beats. A whole
note (semi-breve) with a dot would be worth six beats and could therefore
only be used in a bar of 6/4 time. In the same
way, a "dotted" quarter-note (crotchet) would have the combined value of
a quarter-note plus an eighth-note (quaver), and a dotted eighth-note would
have the same value as an eighth-note plus a sixteenth-note.
Dots can also be added to rests. The principle
is exactly the same: the dot increases the time-value of the rest by half.
See the example shown.
Source: The Guitar
Handbook by Ralph Denyer
INSTRUCTIONS AND ANNOTATIONS