Conversely, when you output something to the console, it first undergoes
the standard tty processing, and then is fed to the console driver.
The console driver emulates a VT100, and parses the input in order to
recognize VT100 escape sequences (for cursor movement, clear screen, etc.).
The characters that are not part of an escape sequence are first converted
into Unicode, using one of four mapping tables if the console was not
in UTF-8 mode to start with, then looked up in the table describing
the correspondence between Unicode values and font positions,
and the obtained 8- or 9-bit font indices are then written to video memory,
where they cause the display of character shapes found in the video card's
character ROM.
One can load one's own fonts into character ROM using setfont.
The obsolete programs loadunimap and mapscrn can be used
to manipulate the Unicode map belonging to the font, or the mapping
table of the console. More details will be given below.
There are many consoles (called Virtual Consoles or
Virtual Terminals, abbreviated VCs or VTs) that share the same
screen. You can use them as independent devices, either to run
indendent login sessions, or just to send some output to, perhaps
from top, or the tail of the system log or so.
See below (`Console switching') on how to set them up and
switch between them.