Hi like to find out what is a control line? And how we find out how
many control line a computer required while writting a machine code?

"Tianfu" <hockz@hotmail.com> wrote in message
news:e8bde602.0312140658.294b6cb0@posting.google.com...
> Hi like to find out what is a control line?

Generally a "control" line is one which doesn't carry data, but carries a
signal which controls the device.

As an example, a simple old-style parallel printer interface will have seven
or eight data lines, for sending the characters to be printed, plus several
other lines to signal things like out-of-paper, ready-for-next-character,
and so on.  Once these arrive at the computer, however, they frequently
become data.  You might read the status port on the printer interface to
find out if the out-of-paper line is active, for instance.

For the processor itself, there are often control lines going out (like
address strobes or read/write selectors) and / or going in (such as wait or
interrupt signals).

> And how we find out how many control line a computer
> required while writting a machine code?

But this makes me wonder if we're talking about the same thing.  I know on a
few assemblers I've used there are so-called "control lines" which are used
to configure the aseembler.  Most folks call them assembler directives or
instructions (because they're instructions to the assembler itself rather
than instructions destined for the computer).  The ORG (origin) statement is
a classic example used in a wide variety of assemblers.  For x86 ones (our
topic here) the ASSUME directive is a good example.

Which sort of control line were you asking about?  Or did you have something
else entirely in mind?

    - Bill