Sun, 27 Nov 2011, 00:14

I received another email with respect to screenshot 2 this evening, so
it looks like I will have to spend a little time dealing with it in
class on Monday.

A student writes:

> Professor Patt,
> 
> Before I ask my question, I will introduce you to my program for the
> pattern. The instructions dictate that there should be delay "each time a
> line is output on the screen". They also that for the user program, TRAP
> instructions are allowed. So for my user program I output a .STRINGZ for
> each line (using TRAP x22) followed by a linefeed then a delay.
> 
> So my question is how can I reproduce example screenshot 2? I can reproduce
> example screenshot 1 because there is a delay between each line's TRAP x22
> instruction, so my interrupt service routine spits out 10 characters of
> whatever I press in-between the two lines. But there is no way I can
> reproduce screenshot number 2, because the TRAP x22 instruction for
> printing out the lines happens too quickly? (Note the question mark)

Thank you for the question mark!

> One way I believe you can solve this is by replicating the function of TRAP
> x22 in your program, and inserting a delay between the display of each
> character in the pattern.

Nope, not necessary.

> If I posses a blatant misconception, excuse my ignorance.
> 
> Thank you for your time,
> <<name withheld to protect the student with a misconception>>

Yes, he possesses a misconception, although I would never call it blatant.

I will also add that you would probably have to run your program many
many times before screenshot 2 shows up.

So, for those of you who have time to think about this between now and
class on Monday:

    1. Why is screenshot 2 possible?
    2. Why will it not happen often?

Yale Patt