Description
Learning GOALS
The purpose of this assignment is to continue practice writing C programs and gain more experience
working in C, a low-level, non-object oriented language. After completing both parts A and B of this
project, you should be comfortable with pointers, arrays, address arithmetic, structures, command-line
arguments, and file I/O in C. For part B, you will also be working with structures and file I/O.
OVERVIEW
For this assignment you will be writing the program myMagicSquare.c, which generates a magic square
of a specified size and writes it to an output file. A magic square is a matrix of size n x n with positive
numbers from 1… n arranged such that the numbers in any line (horizontal, vertical, and both main
diagonals) sum to the same values. You can read more about magic squares in
https://en.wikipedia.org/wiki/Magic_square (https://en.wikipedia.org/wiki/Magic_square)
Like p2A, this project requires you to work with a dynamically allocated 2D array (heap allocation), and
you are not allowed to use indexing to access the array that is used to represent the matrix. Instead,
you are required to use address arithmetic and dereferencing to access it. Submitting a solution using
only indexing to access the matrix will result in a 50% reduction of your score. You may use indexing
to access any other arrays that might be used by your program.
You’re welcome to develop the solution in two phases. First, code a solution that uses indexing. Once
you have that solution working, you can copy and edit to replace the indexing syntax with pointer
arithmetic before final testing and submission. You are strongly encouraged to use incremental
development to code your solution rather than coding the entire solution followed by debugging that
entire code. Incremental development adds code in small increments. After each increment is added,
you test the new code to ensure that it works as desired before adding the next increment of code. Bugs
are then easier to find since they’re more likely to be in the new code increment rather than the code
you’ve already tested.
SPECIFICATIONS
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2020/12/16 p2B: My Magic Square
https://canvas.wisc.edu/courses/205087/assignments/934454 2/7
You are to develop your solution using the skeleton code in the file myMagicSquare.c found on the CS
Linux computers at:
/p/course/cs354-deppeler/public/code/p2B/myMagicSquare.c
The program myMagicSquare.c is run as follows:
./myMagicSquare
Where is the name of the file where the generated magic square is to be written. The
format of the output file will be as follows (also see example run below):
The first line will contain a positive integer, n, that is the size of the matrix.
Every line after that represents a row in the matrix, starting with the first row. There will be n such
lines where each line has n numbers (columns) separated by commas.
Every number in the matrix will be unique.
The program prompts and reads input from stdin to get the size of the magic square to generate. The
program only generates magic squares of odd dimensions like 3×3 or 5×5. You may assume that the
user will input an integer. However, the program must check that the input is an odd number greater than
or equal to 3, and if not, print the appropriate message and exit as shown in the sample run below.
Siamese Method
Read about the Siamese method (https://en.wikipedia.org/wiki/Siamese_method) (← read the
link) to generate the square matrix of an odd size with the numbers 1… n .
Start by placing 1 at the center column of the topmost row in the square, and then for every
number till n
Move diagonally up-right, by one row and column, and place the next number in that position.
Wrap around to the first column/last row if the move takes you out of the square.
If the next position is already filled with a number then place it one row below the current
position.
Alternate Siamese Method
Alternatively, and to make the modular arithmetic easier, you can consider the reflection variant of
the above Siamese algorithm by starting from the central row in the last column and then
moving in a down-right diagonal fashion. Then, follow the pattern described above.
Finally, the program must write the alternate magic square to the output filename specified in the
command line.
The sample runs below show the program’s expected behavior:
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2020/12/16 p2B: My Magic Square
https://canvas.wisc.edu/courses/205087/assignments/934454 3/7
[deppeler@liederkranz] (88)$ ./myMagicSquare
Usage: ./myMagicSquare
[deppeler@liederkranz] (89)$ ./myMagicSquare magicSquare1.txt
Enter magic square’s size (odd integer >=3)
1
Size must be >= 3.
[deppeler@liederkranz] (90)$ ./myMagicSquare magicSquare2.txt
Enter magic square’s size (odd integer >=3)
2
Size must be odd.
[deppeler@liederkranz] (91)$ ./myMagicSquare magicSquare3.txt
Enter magic square’s size (odd integer >=3)
3
[deppeler@liederkranz] (92)$ cat magicSquare3.txt
3
4,3,8
9,5,1
2,7,6
HINTS
Using library functions is something you will do a lot when writing programs in C. Each library function is
fully specified in a manual page. The man command is very useful for learning the parameters a library
function takes, its return value, detailed description, etc. For example, to view the manual page
for fopen, you would issue the command “man fopen”. If you are having trouble using man, the same
manual pages are also available online. You will need these library functions to write this program. You
do not need to use all of these functions since a couple of them are just different ways to do the same
thing. We encourage you to refer to our code in the p2A code skeleton for an example of file I/O.
fopen() to open the file. Make sure you specify the correct mode (read or write) for which you are
opening the file.
malloc() to allocate memory on the heap
free() to free up any dynamically allocated memory
fgets() to read each input from a file. fgets can be used to read input from the console as well, in
which case the file is stdin, which does not need to be opened or closed. An issue you need to
consider is the size of the buffer. Choose a buffer that is reasonably large enough for the input.
fscanf()/scanf(): Instead of fgets() you can also use the fscanf()/scanf() to read input from a file or
stdin. Since this allows you to read formatted input you might not need to use strtok() to parse the
input.
fclose() to close the file when done.
printf() to display results to the screen.
fprintf() to write to a file.
atoi() to convert the input which is read in as a C string into an integer
strtok() to tokenize a string on some delimiter. In this program the input file for a square has every
row represented as values delimited by a comma. See here
2020/12/16 p2B: My Magic Square
https://canvas.wisc.edu/courses/205087/assignments/934454 4/7
(http://www.tutorialspoint.com/c_standard_library/c_function_strtok.htm) for an example on how to
use strtok to tokenize a string.
REQUIREMENTS
Your program must dynamically allocate (i.e., on the heap) the matrix structure and matrix array.
Your program must use address arithmetic and dereferencing to access the array representing the
matrix.
Your program must use the -> operator when accessing data members of a structure via a pointer
variable.
Your programs should operate exactly as the sample run above.
Your program must print error messages exactly as shown in the sample run above, and then
call exit(1).
Your program must check the return values for errors of the library functions, malloc(), fopen(), and
fclose(). Handle errors by displaying an appropriate error message and then calling exit(1).
Your program must properly free up all dynamically allocated memory at the end of the program.
Your program must close any opened files when it’s done using them.
Your program must follow style guidelines as given in the Style Guide.
Your program must follow commenting guidelines as given in the Commenting Guide.
We will compile your programs with gcc -Wall -m32 -std=gnu99 on the Linux lab machines. So your
program must compile there, and without warnings or errors.
SUBMITTING & VERIFYING
SUBMISSION FOR p2B HAS BEEN ENABLED.
Leave plenty of time before the deadline to complete the two steps for submission found below.
There is a 33 minute grace period after the deadline for last minute emergencies. Submitting during this
grace period results in your submission being marked late but it will be accepted for grading without
penalty. No submissions or updates to submissions are accepted after this grace period.
1.) Submit only the file listed below under Project p2B in Assignments on Canvas. Do not zip,
compress, or submit your file in a folder.
myMagicSquare.c
Repeated Submission: You may resubmit your work repeatedly so we strongly encourage you to use
Canvas to store a backup of your current work. If you resubmit, Canvas will modify your file names by
appending a hyphen and a number (e.g., myMagicSquare-1.c).
2.) Verify your submission to ensure it is complete and correct. If not, resubmit all of your work
rather than updating just some of the files.
Make sure you have submitted all the files listed above. Forgetting to submit or not submitting
one or more of the listed files will result in you losing credit for the assignment.
2020/12/16 p2B: My Magic Square
https://canvas.wisc.edu/courses/205087/assignments/934454 5/7
Project p2B
Make sure the files that you have submitted have the correct contents. Submitting the wrong
version of your files, empty files, skeleton files, executable files, corrupted files, or other wrong files
will result in you losing credit for the assignment.
Make sure your file names exactly match those listed above. If you resubmit your work, Canvas
will modify your file names as mentioned in Repeated Submission above. These Canvas modified
names are accepted for grading.
2020/12/16 p2B: My Magic Square
https://canvas.wisc.edu/courses/205087/assignments/934454 6/7
Criteria Ratings Pts
6.0 pts
6.0 pts
3.0 pts
6.0 pts
3.0 pts
6.0 pts
5.0 pts
5.0 pts
5.0 pts
5.0 pts
1. Compiles without
warnings or errors
6.0 pts
No warnings
or errors
3.0 pts
Incorrect output format
Please refer to the project
page on Canvas
0.0 pts
One or more errors or at
least 5 warnings
2. Follows
commenting and
style guidelines
6.0 to >0.0 pts
Followed
0.0 pts
Not followed
3. Implements CLA
checking
3.0 pts
Meets
specifications
2.0 pts
Minor problem
Error message
does not match
specification
1.0 pts
Major problem
Incorrect argc check, no
error message displayed, or
does not exit
0.0 pts
Does
not
check
CLAs
4. Checks return
values of malloc()
and fopen()
6.0 pts
Checks all
3.0 pts
Checks some
0.0 pts
Checks none
5. Closes all opened
files – fclose()
3.0 pts
Closed
2.0 pts
Some closed
0.0 pts
None closed
Execution test: frees
heap memory
6.0 pts
Freed
0.0 pts
Not all freed
Execution test: size =
3
5.0 pts
Correct result
0.0 pts
Incorrect result
Execution test: size =
7
5.0 pts
Correct result
0.0 pts
Incorrect result
Execution test: size =
11
5.0 pts
Correct result
0.0 pts
Incorrect result
Execution test: size =
13
5.0 pts
Correct result
0.0 pts
Incorrect result
2020/12/16 p2B: My Magic Square
https://canvas.wisc.edu/courses/205087/assignments/934454 7/7
Total Points: 60.0
Criteria Ratings Pts
5.0 pts
5.0 pts
Execution test: size =
17
5.0 pts
Correct result
0.0 pts
Incorrect result
Execution test: size =
19
5.0 pts
Correct result
0.0 pts
Incorrect result
