Three important bits of information are displayed in the mode line. these are the buffer name, the file name, and the buffer changed flag.
A window is always displaying a buffer. The name of the buffer being displayed in the window is shown in the mode line, right after the MicroEMACS.
A buffer may have a file associated with it. Usually this is the last file read into or written from the buffer. If a file is associated with the buffer, the name of the file is displayed in the mode line, prefixed by File:. On operating systems in which file names are case insensitive (for example, VMS) the file name will always be in lower case.
MicroEMACS knows if a buffer has been changed since it was last
written to its associated file. It informs you of this fact by displaying
a * in the mode line immediately to the left of the MicroEMACS
string.