11/27/2006

A student writes:

        Dr. Patt,

        In class today you went over stacks, and when you got to the point with
        "JSR ADD" as a line someone recognized the error in that line.  You
        changed it to "JSR Add".  Correct me if I am wrong but wouldn't that still
        be a problem with the LC-3 becuase it case doesnt matter using the
        assembler?  Wouldn't it just be better to name that subroutine "SUM", it
        still conveys the purpose and has no chance of causing an error?  Just a
        thought for future reference.

        <<name withheld to protect the student experienced with the case not mattering>>

Yup, I should know better than to try to be cute in class.  It turns out some 
Assemblers will be case-sensitive, some not.  If it is case sensitive, and the
opcode is ADD, then you are free to use Add as a label.  The problem is, as the
student correctly points out, that for most assemblers the case does not matter.

So, I should have used something like SUM, as he suggested.  But, at the moment,
I decided to be cute, and in so doing provide a problem for all students who
have had experience with software that does not care about upper or lower case.

Shame on me!

I apologize.

Change your notes to SUM.

Yale Patt