CMSC 106 | Project #3 - Gemstones | Spring 2003 |
In this project you will write a program using loops and nested loops. Although as a matter of style and clarity it is usually extremely important to use the most appropriate type of loop for each iterative task in a program, in order to get practice with all of C's loop statements, we suggest that you intentionally use some of each type in your project.
You are developing a game program which uses gemstones of various shapes. Unfortunately, your order for a graphics terminal has been delayed, because all available graphics chips are being used to construct slot machines. So, you decide to draw your shapes using patterns of asterisks.
Your program will use asterisks to draw any size versions of triangles, diamonds, parallelograms, and trapezoids. It will also draw the shapes with rotations in multiples of 90 degrees. Here are some non-rotated shapes with base width 11:
Triangle * *** ***** ******* ********* *********** Diamond * *** ***** ******* ********* *********** ********* ******* ***** *** * Parallelogram *********** *********** *********** *********** *********** *********** *********** *********** Trapezoid ***** ******* ********* ***********
There are some restrictions on the dimensions of the various shapes. These will be descrbed below. It is important that you use the exact style given for each shape in your output.
The input to your program is to consist of a sequence of input lines (redirected from an ASCII text file using standard UNIX input redirection). Each line will contain 4 integers. These will be:
There are some restrictions on the values which may be used. They are listed under "Error Checking" below.
As an example, suppose the program receives the following line of input:
3 11 8 0
This instruction says: ``Draw shape code 3 (parallelogram), sized so that it is 11 wide by 8 high, and rotate the shape 0 degrees before drawing it. (This is the command which could be used to draw the parallelogram shown above.)
The last line in the input will always contain a shape code of -1; it may or may not contain other data items. This is the signal that the program should terminate. (Do not try to draw anything or print any error messages when this line is processed.)
VALID RANGES:
shape code: 1 through 4 (inclusive)
size:
(int) base / 2 + 1
rotation: any multiple of 90
IMPORTANT: You will output AT MOST one error message for each line processed (even if more than one of the values is out of range.) In other words, there will be exactly one error message for each line that contains an error. Below are instructions on how to prioritize your error messages.
First check if the shape code is out of range. If it is out of range, you will print the error message below and move on to the next line in the input. (DO NOT PRINT MORE THAN ONE ERROR MESSAGE, EVEN IF THE SIZE AND ROTATION VALUES ARE ALSO OUT OF RANGE.)
ERROR: ILLEGAL SHAPE CODE
Assuming that the shape code is in the correct range, you will next check the base size entered. If the base size entered is not valid, you must print the message below, and move on to the next line in the input. (DO NOT PRINT MORE THAN ONE ERROR MESSAGE, EVEN IF THE HEIGHT AND ROTATION VALUES ARE ALSO OUT OF RANGE.)
ERROR: ILLEGAL BASE
Assuming that the base size is in the correct range, you will next check the height entered. If the height entered is not valid, you must print the message below, and move on to the next line in the input. (DO NOT PRINT MORE THAN ONE ERROR MESSAGE, EVEN IF THE ROTATION VALUE IS ALSO OUT OF RANGE.)
ERROR: ILLEGAL HEIGHT
Assuming that the shape code and size values are all in the correct range, you must still check that the rotation value is acceptable. If it is not a valid rotation amount, you must print the message below, and move on to the next line of input.
ERROR: ILLEGAL ROTATION AMOUNT
Here are some specific instructions on drawing the shapes:
Below is the primary input file that we are providing:
1 9 5 90 3 4 7 0 2 5 5 0 1 1 1 0 4 5 2 0 -1 -1 -1 -1
* ** *** **** ***** **** *** ** * **** **** **** **** **** **** **** * *** ***** *** * ERROR: ILLEGAL BASE *** *****
cc -std1 -trapuv
on the OIT
UNIX Class Cluster. You will lose credit if your program generates any
warning messages when it is compiled. Even if you already know what they
are, you may not use any C language features other than those introduced
in Chapters 1 through 6 of your textbook, plus those presented in lecture
while these chapters were covered. Note that as a result character variables,
arrays and user-defined functions may not be used. In addition, neither the
goto
nor the continue
statement may be used, and the
break
statement may not be used in any loop. Lastly, your program
must contain only one single return
statement at its end, and may not
use the exit()
function at all. Using C features not in these
chapters, or using the goto
statement, multiple
return
s, or break
or continue
in loops will
result in losing credit.
Your program must have a comment near the top which contains your name, login ID, student ID, your section number, your TA's name, and an original description of the action and operation of the program. Your program should be written using good programming style and formatting, as discussed in class and throughout your textbook. For this project, style is considered to consist of:
Your project must be electronically submitted by the deadline stated above to avoid losing credit per 24 hours as indicated on the syllabus. No project more than 48 hours late will be accepted without prior permission or a valid medical excuse, as described on your syllabus. Lost passwords or other system problems do not constitute valid justifications for late projects. You should start working on your project now!
You may want to skip this section at first, read the rest of the project, and come back to study it carefully when you are about to begin writing your program.
One of the important skills which must be learned in this course is how to track down the causes of and fix both syntax and semantic errors in your code. As your program will inevitably have many errors while you are developing it, you will need to follow procedures such as those described below before coming to office hours for assistance. Should you still not be able to solve the problem and have to come to office hours, you will be required to clearly describe your error and what you have already done to try and find it, and bring current printouts of your source code, and any compiler errors or execution results.
As mentioned in the earlier project assignments it is extremely important to type in only a part of your program at a time and compile and test it to verify that it is correct before going on. Different choices can be made in selecting which parts of a program to implement first; the following is just one possibility. It's fine if you prefer to follow different steps, but whichever order you choose to develop your program it is essential to enter small parts at a time and test each one before going on!
Be sure to compile and thoroughly test the code implementing this step (in fact, you could implement this step itself in several substeps, testing each as you go). These substeps could include assuming at first that the user will only ask for a triangle. Then a parallelogram, and so on. You may want to assume that the rotations are all 0 until you are able to print all shapes in their usual orientation first. Take each step allowing more flexibility in the input - make sure you have the correct values in your input file for the development level you are assuming at that time.
A useful strategy to use for narrowing down the cause of such
types of errors is to comment out one section of the program at a
time and recompile it after each part is commented out, until the
syntax error goes away. At that point, the cause of the error
must be in the most recently commented-out code. If you comment
out parts of your code your program certainly won't work
correctly, but this technique is just to help you quickly find the
syntax error, and once you correct it you can just remove the
/*
and */
symbols which you added to comment out
your code.
A few things to keep in mind about this technique are as follows.
You can't comment out only a part of a larger statement, for
instance, you can't comment out the first half of an if
statement but leave the else
part- you would have to
comment out the whole if
/else
. You can't comment
out half of a compound statement such as the opening brace
({
) and some of the statements inside but leaving the
closing brace (}
) uncommented as part of the code- you
would have to comment out the whole compound statement. You also
can't comment out code containing comments- you would have to
copy your program to a different file, delete the comments, and
then use this strategy. Once you find the syntax error in this
temporary copy of your program you can correct it in your real
version.
A file used for UNIX input redirection (using the <
symbol after
the name of a program being run) is just a text file which you can create
with any UNIX text editor (e.g., emacs). You type the exact lines to be
used for the program's input the same way you would have typed them from the
keyboard while the program was running if you were not using input
redirection. To run the program with different input you can modify the
file or create a new one with different contents.
The newline character will not be visible at the end of each line of the input file you create. It is necessary that there be a newline character at the end of the last input line, so be sure you press the return (or enter) key at the end of the last line of any file you create containing input values you are going to test your program with. Otherwise your program may not work properly in some circumstances.
printf
statements. Since you are writing a program to draw something,
the debug printf
output will prevent your output from being
displayed correctly, but it can help you figure out why your
program is wrong and the debug printf
s can be easily
removed after that.
printf
statement inside the body of each loop and run your program again,
the printf
which gets repeated identifies which loop is the
infinite one. If no line gets repeated, the infinite loop was
either missed when you added the debug printf
s or this loop
does not have a body. An extra (unwanted) semicolon in the wrong
place can cause the loop to have a null (empty) statement for its
body.
printf
statements and you didn't see their results
printed, so the problem would seem to be above that point in the
program. However, it could be that those statements were
executed, but their results were just not displayed on the screen
because the infinite loop or fatal error occurred soon afterwards
in the program.
It may sound like it's a difficult debugging problem to even
figure out where in your program an error occurs, if printf
results may or may not appear on the screen, but there is an easy
way to see all of a program's output at any time. If a newline
character (\n
) is printed, then any pending output which
has not actually been displayed yet will be immediately printed.
So if your program seems to have an infinite loop (or a fatal
error), either simply print some newlines, or even better, as
mentioned above, add debug printf
statements to every loop
to see which one has the problem- but make sure each such debug
printf
ends in a newline character! Extra newlines or
debug printf
results will probably cause your output to
appear incorrect, but at least they will help you figure out where
your program's error is, and the extra print statements can be
easily removed later.
If there is any chance you may ever have to come to office hours, you should make your code readable from the very beginning. You should be able to easily understand it, and so should your instructor or a teaching assistant in office hours. If your code is a mess, the teaching assistants will direct you to first clean it up before returning so they can understand it and be able to help you. Naturally you want your code to be clear and easily readable by the graders after you have submitted it as well.
Any evidence of unauthorized use of computer accounts or cooperation on projects will be submitted to the Student Honor Council, which could result in an XF for the course, suspension, or expulsion from the University. Projects are to be written INDIVIDUALLY. For academic honesty purposes, projects are to be considered comparable to a take-home exam. Any cooperation or exchange of ideas which would be prohibited on an exam is also prohibited on a project assignment, and WILL BE REPORTED to the Honor Council.
VIOLATIONS OF ACADEMIC HONESTY INCLUDE:
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IT IS THE RESPONSIBILITY, UNDER THE UNIVERSITY HONOR POLICY, OF ANY STUDENT WHO LEARNS OF AN INCIDENT OF ACADEMIC DISHONESTY TO REPORT IT TO THEIR INSTRUCTOR.
Turn in your program using the ``submit'' program as before, except using ``3'' for the project number. You are to submit only the .c file containing your source code, not the executable version of your program! If your program is in a file named p3.c, submit would be run as shown. Don't forget to read the class announcements in your instructor's account every time you log in.
Before you submit your project, you must exactly follow the specific submission checklist in the ``Testing projects before submitting'' handout separately posted by your instructor!