I just copied this definition off the web, idk if it helps (airspaces are not interesting, especially to non pilots): Identify Class Charlie (C) airspace with a magenta circle on sectional charts (see figure 4). Similar to Class B, Charlie altitudes are given in MSL with the last two zeros omitted, but they can be differentiated by their magenta color (see figure 5). If Class C airspace underlies Class B, the ceiling is depicted with a âTâ for top which lies just under the beginning of the Bravo. SFC is a typical floor altitude stating the Charlie in that sector begins at the surface (see figure 6). The name of the Charlie is also given (i.e.,). Any specific regulations or notes are enclosed in magenta boxes and often include approach or control radio frequencies to be used by arriving aircraft to establish communication with ATC before entering Class Charlie (see figure 7). At some airports, the communication frequencies do not operate 24/7. To notify aircraft of this occurrence in this and other airspace classifications, the airport issues NOTAMs (notices to airmen) and/or has a published schedule in the Chart Supplement (previously known as the A/FD). When approach control closes in any airspace, that airspace reverts to class Delta, and without an active tower frequency, class Echo.
