t unpacked_s {
    struct modes_s modes;
    uint8_t opcode : 4;
    uint8_t regc   : 4;
    uint8_t regb   : 4;
    uint8_t rega   : 4;
};
</pre>
</div>

<p>
The immediate value follows the instruction in memory; the emulator fetches it
upon execution.
</p>
</div>

<div id="outline-container-sec-3-1" class="outline-3">
<h3 id="sec-3-1">Decoding</h3>
<div class="outline-text-3" id="text-3-1">
<p>
With the knowledge of the instruction format and its in-emulator representation,
it is not difficult to write a 