The Printer Charset file format (P24, P9, L30)

The printer file format is a variant of the Editor Charset file format (E24) and, apart from the magic bytes at the start of the file is the same across all printer types:

• ps24 for the 24-needle printers (*.P24 files)
• ps09 for the 9-needle printers (*.P9 files)
• ls30 for the laser printers (*.L30 files)

+-----+-----+-----+-----+
|  four character code  |
+-----+-----+-----+-----+
| "0" | "0" | "0" | "1" |
+-----+-----+-----+-----+
|       font type       |
+-----+-----+-----+-----+

For all fonts I have tried, the font type is 0x00000010, which is big-endian for 128. That corresponds to the default 7-bit character fonts used in Signum! 1/2.

127-character fonts

The header is followed by 128 bytes of something.

After that, there is a big-endian 32-bit byte-length specifier for the character data buffer, which is the largest and last part of the file.

After that length, there are 127 BE, 32bit offsets into the character buffer, that correspond to the 127 characters. This may be used for random access to any of the characters.

Finally, there is the character buffer itself, which is a sequence of 4 byte character headers and a variable amount of bitmap data.

+--------+--------+
|  top   | height |
+--------+--------+
| width  |  ???   |
+--------+--------+
|        .        |
+        .        +
|        .        |
+-----------------+

That last character header byte is probably just padding. The number of bitmap rows is height, width is the number of bytes in a row. top indicates the distance of that bitmap from the upper edge of the line.

For the mapping between character codes and keys on the keyboard, have a look at the character sets page.