11.6.1 BZR format introduction

This section describes some general conventions of the BZR format.

In the following sections, we use the notation name[n] to mean that some constituent name of the BZR file takes up n bytes. If name is all capital letters, it is an opcode, i.e., a command byte, and therefore we give no [n] after name, since all opcodes are a single byte. The numerical value of each opcode is given in the source file `bzr/bzr_opcodes.h'.

Some values in BZR files are "pointers". These values give the location of some other byte in the file. The first byte is numbered 0, the next byte numbered 1, and so on.

Besides commands which actually define the font, the BZR format has a NO_OP command, which does nothing. Any number of NO_OP's can occur between the preamble and the character definitions, between character definitions and commands within characters, between the character definitions and the postamble, and after the postamble. But they may not occur within the preamble, the postamble, or between a command and its parameters.

Besides simple integers, BZR format uses a fixed-point representation of real numbers called a scaled, which is three bytes: two bytes of fraction and one byte of integer. We can get away with such a small range because almost all numbers are scaled by the design size; i.e., in a 10-point font, a designsize-scaled value of 1.0 would represent 10 points (quite a large distance, relatively speaking).

In fact, designsize-scaled numbers are typically less than 1.0, so the BZR format provides for abbreviating such, thus making the font smaller, as detailed in the following sections.

Negative numbers are represented in 2's complement notation, and multibyte values are stored in BigEndian order, regardless of the conventions of the host computer. This makes a BZR font file portable between different architectures.