We have already written parts of the program for you. You must use this exact code as your starting point. To save typing, our starter code is available online through the course web page located at http://www.cs.utoronto.ca/
dianeh/148.html
Due electronically: Thursday 26 September, 6:00 pm
This assignment is worth 1 mark towards your grade in this course.
Part marks will count.
Introduction
This is a warm-up assignment
to get everyone going, particularly students
who
aren't familiar with the Turing programming language.
This
assignment should be straightforward for all CSC148 students.
If you don't find it so, then you might need more programming
experience before taking 148;
consider changing to CSC108.
The problem
Imagine that you want a Turing program that determines whether a given integer
is divisible by 11. This can be easily accomplished using ``mod 11'',
but only if the integer is small enough to be stored in a Turing
int. What if the integer is, say, 50 decimal digits long?
This is more than a Turing int can hold.
(You can print out maxint to see the largest int Turing
can hold on your system.)
Some other representation for the integer will be required.
There are many possibilities. One of the simplest is to use an array
of ints, each of which stores a single digit of the integer to
be tested, with the most significant digit stored in array position 1.
Along with this, the number of digits must be stored.
Now the problem is how to test for divisibility by 11, because mod only works on ints. The following method can be used:
Your task is to write a program that reads in a series of positive integers
and uses the representation and method described above to determine,
for each, whether or not it is divisible by 11.
Each integer will be on a separate line,
and may be up to 50 digits long.
Integers will not be prefixed by a ``+'' sign or leading zeros.
You may assume that there are no errors in the input, such as
illegal characters, or integers greater than 50 digits in length.
The output will be a single line for each integer, giving the appropriate
one of these messages:
The number number is divisible by 11.
The number number is not divisible by 11.
How to write your program
We have already written parts of the program for you.
You must use this exact code as your starting point. To save typing,
our starter code is available online through the course web page
located at
http://www.cs.utoronto.ca/ dianeh/148.html
(You will also find there an example of an input file
and the output that it should produce.)
Make your own copy of the starter code using your web browser.
(With Netscape, you can use the
``Save As'' command under the ``File'' pull-down menu.)
Then edit the program and insert the missing pieces in the places marked
by >> and <<.
You must use our starter code, and
you must not make any alterations to it.
In particular, do not change the subprogram headers and do not change
the input or output statements.
Do not add prompts for the input.
How to hand in your assignment
For this assignment,
your solution will be marked by a computer program,
which will put it through a thorough set of
test cases.
We will not tell you what these tests are.
Because the assignment is simple, the marking scheme
will be tough.
You should therefore test your code very thoroughly
before handing it in.
Because this assignment is to be marked by a program,
you will hand it in electronically rather than
on paper.
Name the file containing your completed program
a0.t.
When you are convinced of the correctness of your code,
hand it in electronically using the ``Hand in (submit)'' command,
found under the ``File Utilities'' icon.
You will asked to choose which file to hand it,
which in this case is a0.t.
If you hand in a solution more than once, we will have only a copy of your
most recent version; our copy of the older ones will
be erased.
The program that will mark your assignment is not terribly
clever,
and can only compare your program's output character for character
with what we tell it is the correct output.
If your output is different in any
way from the expected output, it will be considered
wrong, and your mark will be zero.
For this reason, we are providing, among other things,
the statements that perform input and output.
If you modify these in any way, or add other input or output
statements
(for example, if you add prompts)
your mark will be zero.
In addition, you must use the file name a0.t when
you hand in your assignment, or your mark will be zero.
Some useful advice
Students who are already familiar with
Turing should need only a couple of hours to complete this assignment.
Students who are not familiar with Turing will need extra
time to learn the details of the Turing language
and programming environment.
The most effective way to get this assignment done quickly is to write
your program out on paper and simulate it by hand before you
go near a computer, in order to get rid of as many errors as possible.
Even if you plan to develop your program at home, you will have to use one
of our PCs
to hand in your final program.
Make sure you log in and get comfortable with our computers well before
the due date.
Try to get your assignment finished early. The computers are likely to
be very crowded near the due date.
About future assignments
This assignment is unusual in comparison to the rest of the assignments
in CSC148.
First,
it is far less difficult
than the assignments to come.
Second, you will hand it in electronically, whereas
future assignments will generally be handed in on paper.
Finally, only the
correctness of your code will be evaluated.
Future programs will be evaluated also for programming style,
documentation, and testing, and will require a report.
These aspects may be worth as much as 75% of future
programming assignments.
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