code table selector
the first character in the text code of CESR stream that determines which code table to use, either a default code table or a code table selector character when not the default code table. Thus the 1 character text code table must do double duty. It must provide selectors for the different text code tables and also provide type codes for the most popular primitives that have a pad size of 1 that appear is the default code table.
See row 1.
