If TYPO encounters an abnormal termination condition,
such as the user exiting out of the window system,
TYPO will checkpoint every font file that was modified and not saved.
If the current character was modified and not saved,
it is checkpointed in an additional single-character font.
A font by the name fontname is checkpointed as
fontname.CKP.
The current character is saved in a font by the name CURRENT_CHAR.CKP.
If a checkpoint font cannot be written into the directory that was active
at the time TYPO was executed, it is written into the /tmp directory.