• FNT Files
• FONT Resources (FON Files)

These files store a proportional character set. FNT files are found in DARK.GOB
This set may not be complete. The font used to display the ammo, for instance contains only the numbers and the ':' character.

FNT_Header IS { Magic char[4] // 'FNT' + 15h (21d) Height byte // Height of the font u1 byte // Unknown DataSize int // Data after header First byte // First character in font Last byte // Last character in font pad1 byte[22] // 22 times 0x00 }

Then follow the characters.
There is (Last-First+1) FNT_Character blocks (one per character).

FNT_Character IS { Width byte // Width of the character Picture byte[Width*Height] // Bytes describing the character, // by columns from bottom to top // Each byte is an index in the // current PAL palette }

These LFD resources store a proportional character set, which may be incomplete.
I found two examples : font6 and font8.

Note
the .fon extension is a convention adopted by add-on developers when writing conversion programs, there are no real FON files in DARK FORCES. There are FNT files however, which are quite different !

FON_Header IS { First int // First character in font Last int // Last character in font u1 int // 8, could be bits per char line Height int // Height of Chars u2 int // could be average Width // or the minimal Width to use pad1 byte[2] // 2 times 0x00 }

Then follows a block of (Last-First+1) bytes (one per character), which code the width of the corresponding character.

FON_Characters_Widths IS { Widths byte[Last-First+1] // each byte is the width // of one character }

Then each character is described in turn:

FON_Character IS { Bitmap Byte[Height] // Height bytes for each // character }

Now the funny part: each of these bytes is a bitmap representation of a line of the character.
A bit set correspond to a pixel drawn on the screen.

For example, if the bytes are 48h, FCh, 48h, FCh, 48h, 00h this gives

48h .X..X... FCh XXXXXX.. 48h .X..X... FCh XXXXXX.. 48h .X..X... 00h ........

Which is the # character.
Note that the width as referenced in the FON_Characters_Widths array would be 6 for this character.
In fact, FON_Characters_Widths must be used to determine where on the screen to draw the next character.