Hello Fernando,
 FA> Suppose I want to make a compiler for the 80x86, and I have to
 FA> compile code such as:
 FA>
 FA>         mov ax, 5633h
 FA>         jmp yeah
 FA>         mov bx, 7896h
 FA>
 FA> yeah:
 FA>         mov cx, 4543h
 FA>
 FA> Well, I don't know how to code the "jmp" instruction, as I don't have
 FA> the address that equals "yeah" label.
Just teasing you a bit with my following comment. Have you noticed that there
are several opcodes for a jmp? If a jmp is closer than 7fh bytes you can use 
two
bytes for the opcode with the offset. If the jmp is closer than 7fffh bytes
you'll need three bytes (opcode and two bytes for offset). And then there is 

jmp-opcode followed by two bytes, defining the direct address.
Writing .COM-files is easy when you use a direct address for every jmp.
In that case you just compile(assemble) the mnemonic to opcodes, collecting 
the
addresses op the labels.
Otherwise you'll have to do several assemble-routines, to check the
offset-differences.
Greeting, Jos Croeze
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