| CMSC 106 | Project #3 | Fall 2001 |
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 determine 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 it is suggested that you intentionally use several types in your project.
You are developing a program to help predict the movement of hurricanes. Because the model you are using does not include the physics of atmospheric motion, the program applies some simple rules which depend on whether the storm is over water or over land. In order to handle different shapes of coastlines, the model uses several simplified patterns of land and water. Starting with a particular map pattern and the initial conditions for the hurricane, the program will print out the predicted movement and strength of the storm. When the hurricane reaches a point where it would move off the edge of the map, the program will print out the map, showing the final position of the storm.
As you read this section, you may also want to refer to the ``Sample output'' section below.
The input to your program is to consist of a sequence of groups of input lines (redirected from an ASCII text file using UNIX standard input redirection). The first line of each group will consist of three integers:
The second line will consist of two integers, the row and column which represent the starting position of the hurricane. The row along the northern (top) edge of the map is row 0, and the column along the western (left) edge of the map is column 0. The program may assume that the row and column values are valid for the current map.
The third line will consist of two integers, the starting barometric pressure in millibars and the wind speed in knots. The program may assume that the pressure and wind speed are correct.
The program will read the input lines and then print out the predicted movement (row and column) of the storm and its strength (barometric pressure and wind speed) until the predicted storm movement would be beyond the edge of the map. The position and strength must be printed in neatly aligned columns, as shown in the sample output. Then the program will print out the map, showing the areas of land and water and the final position of the storm. The program will continue reading input lines and printing storm predictions and maps until it reads an input line which contains a map type of 0. The last line will be complete (contain 3 values), but the program will do no further processing once that line is read.
Valid map types, their descriptions, and examples are the following:
Map type 1 has a north-south coastline located in the middle of the map. Land (indicated by '*') is on the west, and water (indicated by '-') is on the east. Because the coastline is exactly halfway between the western edge of the map and the eastern edge of the map, the number of columns for type 1 must be even.
*****----- *****----- *****----- *****----- *****----- *****----- *****-----
Type 2 has a coastline which goes diagonally from the northwest corner to the southeast corner. All of the points directly on the diagonal are land. In order to simplify the calculation for the location of the diagonal, type 2 must be a square (number of columns equals number of rows).
*--------- **-------- ***------- ****------ *****----- ******---- *******--- ********-- *********- **********
Type 3 is similar to type 2, but it has a coastline which goes diagonally from the northeast corner to the southwest corner. All of the points directly on the diagonal are land. In order to simplify the calculation for the location of the diagonal, type 3 must be a square (number of columns equals number of rows).
********** *********- ********-- *******--- ******---- *****----- ****------ ***------- **-------- *---------
Type 4 has a triangular shape of land, where the easternmost point is in the middle of the map. Note that the size of the dimensions must be odd (as it is in this example), in order to have a properly shaped triangle. All of the points along the edge of the triangle which are also on a diagonal of the square are over land. In order to simplify the calculation for the location of the coastline, type 4 must be a square (number of columns equals number of rows). Also, the number of rows and columns must be odd.
*-------- **------- ***------ ****----- *****---- ****----- ***------ **------- *--------
Type 5 has a triangular-shaped bay of water, where the westernmost point of the bay is in the middle of the map. Note that the size of the dimensions must be odd (as it is in this example), in order to have a properly shaped triangle. All of the points along the edge of the triangle which are also on a diagonal of the square are over land. In order to simplify the calculation for the location of the coastline, type 5 must be a square (number of columns equals number of rows). Also, the number of rows and columns must be odd.
********* ********- *******-- ******--- *****---- ******--- *******-- ********- *********
Hint: For drawing map type 4 or 5, look for a relationship with types 2 and 3.
All of the land points on the map are to be printed using '*' and all of the water points are to be printed using '-'. Note that the "square" maps will not actually appear square when they are printed, since the height of a printed row is greater than the width of a character. No map can be printed which has more than 20 rows or 30 columns.
If any group of input lines contains an incorrect map code your program must print an explanatory error message and read a new group of input lines without processing the data values for the incorrect map. This explanatory error message must be printed all on one line and contain the exact word ``ERROR'' followed by the two words ``Map Code'' followed by the invalid input value.
If the map code is valid, but the input line contains an invalid set of map dimensions, your program must print an explanatory error message without processing the data values. This error message must be printed all on one line and contain the exact word ``ERROR'' followed by the word ``Size'' followed by the invalid input values. If both the map code and map dimensions are invalid, then only the message for the map code is to be printed.
Before each set of output (hurricane forecast or error message), a line must be printed to tell the person who is reading the output which set of input lines the output that follows corresponds to. The line must first have an integer (starting with 1 for the first set of input lines) followed immediately by a space which is then followed by a series of exactly 20 plus signs ('+'). This line must be followed by a blank line.
Following the output header message, the program must print the forecast for the hurricane's movement and strength, followed by a map which shows the hurricane's final position. The forecast is determined by the following rules:
Following the list of storm positions and strength, the program must print a blank line. Following the blank line, the program must print a map of the correct size showing the location of land and water points. The final position of the hurricane must be shown with a zero ('0'). The rows are to be labeled, starting with 0 in the north (top). There is to be a single space between the row labels and the points in a row. The columns are to be labeled, starting with 0 in the west (left). Note that if the column number is more than 1 digit, the label must be arranged vertically, since the width of the columns is only 1 character.
The program must continue reading and processing groups of input values until the end of the input is reached as described earlier.
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 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
returns, 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. Do not put your alias in this comment! 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 the user will only ask for the first type of map. Take each step allowing more flexibility in the input - make sure you have the correct values in your input file for whichever 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 map from being
displayed correctly, but it can help you figure out why your
program is wrong and the debug printfs 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 printfs 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 storm.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.
% submit 3 storm.c
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!
If the name of the executable version of your program is storm.x, here is a sample execution for the input data shown. Each of the three sample sessions show the input file and then what the program does when run with that input file. The first column is what we will be grading as the primary input - the other two are just to show other output for more advanced features of your program.
Be sure to test your program against a variety of data, so you are sure it works in all circumstances!
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