GNAT Reference Manual
8.5.3 Get_Immediate
Get_Immediate returns the next character (including control characters)
from the input file. In particular, Get_Immediate will return LF or FF
characters used as line marks or page marks. Such operations leave the
file positioned past the control character, and it is thus not treated
as having its normal function. This means that page, line and column
counts after this kind of Get_Immediate call are set as though the mark
did not occur. In the case where a Get_Immediate leaves the file
positioned between the line mark and page mark (which is not normally
possible), it is undefined whether the FF character will be treated as a
page mark.
