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Re: 6502 illegal opcodes questions



fred mueller wrote:
Paul Schlyter wrote:

In article <S6mdnYNMG-caHhnZnZ2dnUVZ_vidnZ2d@comcast.com>,
Michael J. Mahon <mjmahon@aol.com> wrote:

Paul Schlyter wrote:

Some programming languages even had these formatting rules built-in.
In e.g. FORTRAN (up to FORTRAN-77), these rules had to be obeyed:

Column 1:      C or * marked the whole line as a comment
Columns 2-6:   Labels went here - 1-5 decimal digits
Column 7: A non-space character here marked this line as a contination line
Columns 8-71:  The program statement went here
Columns 72-80: Comment - anything here was ignored by the compiler

Actually, it was:

Column 1-5:    Statement number, or "C" in column 1 for comment lines
Column 6:      Non-blank marks continuation line (often 1-9 to indicate
                sequence of the continuations if more than one)
Columns 7-72:  FORTRAN Statement
Columns 73-80: ID/sequence field, ignored by compiler


Thanks for the correction. Yep, my fortran skills are getting rusty -- it's some
20 years since I last coded in that language.


If you think you are rusty, its been 45 years for me and on an IBM 7094 mentioned below. And just think that was state of the art then. It was fun getting the back together if you were clumsy and dropped it. Speaking from experience :-).

The sequence field was often left blank on manually keypunched cards,
but was almost always filled with some combination of a "deck" ID and
a sequence number on machine-punched decks, as were "binary" decks.

I remember many times using an IBM 82 card sorter to restore order
to a deck containing gravity-induced entropy.  ;-)

I think most people who used punched cards had the experience of
dropping a deck at one time or another!  And if it wasn't a dropped
deck, it was a reader jam and subsequent imperfect recovery.

I habitually used a Magic Marker to make a diagonal stripe across the
top of my deck after making any changes, using different colors and
locations for the stripes over time.  That is a very simple way to
"sequence" a deck, and provides instant visual verification that the
cards are in the intended order.

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."