# $ K + UFM Editor Window
Each UFM editor window displays the contents of a single .ufm file. Each .ufm file describes a device-resident font. Font descriptions consist of a set of C-language structures. Each tab in the editor window allows you to view and modify the contents of one or more of these structures.
All .ufm file structures are described in the Windows 2000 DDK. You can find each structure's name in the DDK index.
Headers Tab
Allows you to modify the .ufm file's UNIFM_HDR and UNIDRVINFO structures.
IFIMETRICS Tab
Allows you to modify the .ufm file's IFIMETRICS structure.
EXT METRICS Tab
Allows you to modify the .ufm file's EXTTEXTMETRIC structure.
Widths Tab
Allows you to modify character widths, in font units, for variable pitch fonts.
Kerning Pairs Tab
Allows you to specify kerning pairs. If the kern amount is a positive value, the two characters are moved further apart; if the value is negative, the characters are moved closer together.

Units for Font Metrics
Scalable fonts are described in arbitrary font units. These units are mapped to master units at the unscaled size of the font, using information on the Scalability Metrics tab. 
For all other fonts, metrics are specified in master units.