) preceded and followed by blank lines, followed
by the output section.
The first line of this output section must contain the phrase
``Results for''.
The following 4 lines must contain the data values read in, as follows:
| CMSC 106 | Project #1 | Spring 2002 |
In this project you are to write a C program which will declare variables, read values into variables, write the values stored in those variables, and perform various calculations and assignments using them.
You want to download some music files and ``burn'' them onto a CD-R. In order to calculate the amount of time and storage space necessary to do the job, you write a program to do the calculations. Your program will prompt the user to enter values telling how much music is being downloaded, and the program will determine the size of the files and the time required to accomplish the task.
You will be required to write a C program to do the calculations explained in this section. As you read this section, you may also want to refer to the ``Sample output'' section below.
Your program is to first print certain introductory information and read certain required input values from the user. It will then print the calculated values, labeling them and arranging them neatly in columns.
Your program must first print a welcome message:
Welcome to "CD Data Wizard"!
The message must be punctuated exactly as shown, including the double quotes.
The program will then prompt the user for a series of input values.
There must be a blank line between any two requests for values.
Your program may assume, without checking, that the user will enter the proper number of values which will be of the types described above and whose values will always be within the ranges indicated.
After the input values are read, your program is to print 10
asterisks () preceded and followed by blank lines, followed
by the output section.
The first line of this output section must contain the phrase
``Results for''.
The following 4 lines must contain the data values read in, as follows:
The data values must be neatly aligned in a column, as shown in the sample output.
Following the list of input values, the program must print the results calculated for 2 different audio data formats, MP3 and Real Media (RM). The set of outputs for each format is printed on a single line, with the values in each line aligned neatly in columns and labeled as shown in the sample output. The output values, in order, are:
All time values must use a colon (
) to separate hours, minutes, and seconds.
Leading zeroes must be used in time values if necessary to avoid having blanks
imbedded in the value.
Values for bytes and seconds must be rounded to the nearest whole unit.
Values for percentage must be rounded to the nearest hundredth of a percent.
Values for maximum number of songs must be rounded DOWN to the nearest whole number.
Output values must be calculated as described in the next section.
Here are the constants and formulas the program must use. Note that you MUST use these EXACT constants and formulas, even though you may know of more accurate values. You MUST also use preprocessor macros (symbolic constants) to define any special constants used in the program.
In this project, you should do any rounding of values only after all
calculations using those values have been made. This means that even
though all input values are int, you will need some float variables
to do the calculations.
You should use float variables (or expressions)
for quantities which may have a fractional part, and int variables
for whole number quantities. Chapters 2-4 of your text don't discuss how
expressions which contain both int and float values are evaluated
(this is covered in detail in a later chapter). In order to avoid any
problems with your calculations, you should realize now that expressions
with both int and float values will have a float value
when computed.
When writing the expressions for the conversions, be aware that doing the statements in a different order can cause you to get a different answer. For example (52/5200) * 100.0 = 0.0 but (52*100.0)/5200 = 1.0. This is because the 52/5200 is calculated as an integer value since both operands are integer. The answer is actually 0.01, but because it is forced into an integer storage location, only the 0 is stored. Then when it is multiplied by 100.0, the answer is 0.0 because any float times 0 is 0.0. When the second expression is evaluated, the 52 * 100.0 makes it 5200.0 (a floating point number), and then when the division happens, the answer is 1 because there was no truncation of the fractional part. If you have two integers and you want to make sure the result is stored in a float, one easy way is to multiply one of the operands by 1.0 before the other operation is done.
All your C programs in this course should be written in ANSI C, which means they must compile and run correctly with ``cc -std1 -trapuv'' on the OIT UNIX Class Cluster. Even if you already know what they are, you may not use any C language features other than those introduced in Chapters 1 through 4 of your textbook, plus those presented in lecture while these chapters were covered. Note that as a result conditional statements or loops of any type may not be used. Using C features not in these chapters 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:
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.
A crucial part of the material to be learned in this course is how to properly develop programs and find the inevitable errors you will make while writing them. This section addresses how to do that. It is not up to the instructional staff to find every error in your program; you need to learn how to find and fix most of them for yourself. If you have tried the techniques below and have still not been able to find or correct a problem, bring a printout of your program (plus printouts of any compiler errors or execution results) to our office hours and we will be able to help you.
Many people like to write their whole program, or at least have a good outline and idea of what it will look like, before sitting down to type any of it in. That's fine, but it is absolutely essential that you never type in more than a short part of your program without stopping to test what you have so far. You should stop and compile your program, run it on sample input, and verify that it works correctly so far before going on to enter the rest of the program! Of course, at each intermediate stage the part of the program you have entered will obviously not solve the whole problem, and it must at least be a complete and valid C program, but you will find that testing your project at each stage of development will insure you can find and fix any errors more quickly and easily.
For instance, even with a relatively short program like this one you might enter or implement it in steps as follows:
printf statements to print the values which were read, to
make sure these values were read and stored correctly. If not,
correct your program before going on!
In fact, you may want to break each of these steps up into smaller steps- to add statements to print only part of each output section at a time.
Many programs can be developed with equal ease in different orders. The specific steps followed are not important; what is crucial is that you stop and compile and test your program after each one.
{ }). Make sure that
there is a closing brace to match the main function's
opening brace. Indenting statements between braces in a readable
manner will assist in this task.
(or scan, or Printf) This means you have
misspelled the name of one of the standard library functions
(printf as print or Print, scanf
as scan, etc.). Every program component must be
spelled exactly, and even one incorrect character will cause
your program to fail to compile. Check every call to these
library functions carefully.
You probably forgot either the opening or closing double-quote
mark in one of your printf or scanf argument
strings.
The cc C compiler requires that a source file's name end in ``.c''. That's a lowercase ``c'', as in a filename like ``proj1.c''. If your program's filename isn't in that format you must rename it.
It is inevitable that many, if not most or all, of your programs will fail to work correctly as initially written. A few simple strategies can help:
printf statements to your program
to print out the values of variables and calculations.
Essentially, this lets the computer trace your program for you.
If the printf statements show that your variables or
expressions don't contain or produce the values you think they do
then that's a clue to what's wrong. Using debug printf
statements you can narrow the problem down and determine which
variables or expressions don't have the proper values, and then
look at those more closely.
float variable which has
never been given a initial value and contains a garbage value. To
check for the first case, add debug printf statements
before every division printing the value of the denominator. To
check for the second one, check carefully that all your
float variables have initial values or that values are
assigned to them or read into them before they are used in
calculations.
printf and scanf. See your lecture notes where this
was discussed, or look at your textbook on pages 39-40.
printf with scanf. See your class notes, or
carefully reread pages 39-40.
Readable code is important in the real world because most of the programmer's time is spent rewriting or modifying code that already exists - not writing code from scratch. To make your code readable, be sure to use descriptive variable names (English words or their abbreviations), indenting (so that you can tell what statements are dependent on others), vertical whitespace (blank lines between sections) and comments for the person reading the code. Even though in this class you will not be rewriting someone else's code, anyone of the instructional staff who reads your code will be able to do so much quicker and the grader will be much more likely to be able to follow your code if you make it readable right from the start.
Remember that the vertical spacing (what appears on each line) is up to you as you type. Emacs does not do a word wrap - so if there is a very long line, you should press the enter key to wrap it to the correct position on the next line to make the code as readable as possible. Points will be deducted for excessively long code lines.
Keep one or two backup copies of your program saved under different filenames or in different subdirectories of your account. Before making any major changes to your program, copy it to a new backup file with a different name. This will save you a lot of time if you accidentally delete your file, or if it turns out that your changes were incorrect and you want to quickly return to the previous version without having to undo all of your modifications by hand.
Always start all your projects as soon as they are assigned! If you end up having a problem which you can't solve on your own you will have plenty of time to come to office hours for help. If you wait until right before a project is due and you run across such a problem it's too late to get help without having to submit your project late and lose credit.
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:
|
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.
Your project must be electronically submitted by the date above, before 11:00 pm, to avoid losing credit as indicated on the syllabus. No projects more than two days late will be accepted for credit without prior permission or a valid medical excuse, as described on your syllabus. Only the project which you electronically submit, according to the procedures provided, can be graded; it is your responsibility to test your program and verify that it works properly before submitting. Lost passwords, power or network outages, or other system problems do not constitute valid justifications for late projects, so do not put off working on your program or wait to submit it at the last minute!
Turn in your assignment using the ``submit'' program provided by your instructor. You are to submit only the .c file containing your source code, not the executable version of your program!
If your source code was in a file named ``cdwizard.c'', submit would be run to turn it in as shown:
% submit 1 cdwizard.c
In order to execute the submit command above you must have previously run the ``setup'' command in your instructor's posting account, as described in discussion section and mentioned again below. If you do not see a message saying your submission was successful, then your project was not turned in. Try again, or come to office hours for assistance.
Before you submit your project, you must exactly follow the specific submission checklist in the ``Testing a project before submitting'' handout separately posted by your instructor!
Here is a sample output, assuming the executable version of the program is in a file named ``cdwizard''. Underlined text is typed in as input when the program is run, while everything else is written as its output. The output would vary if different values were entered for any of the underlined input values. Be sure to test your program against a variety of inputs, so you are sure it works in all circumstances!
% cdwizard
Welcome to "CD Data Wizard"!
Enter connection speed (bps): 9600
Enter song length in time (min, sec): 4 30
Enter number of songs: 12
Enter CD-RW write speed (units of x): 2
**********
Results for
Connection speed: 9600 bps
Song length: 4:30
Number of songs: 12
CD-RW write speed: 2x
Bytes Download time Record time Total time Percent used Max songs
MP3 39852000 9:13:30 2:10 9:15:40 5.85% 205
RM 38070000 8:48:45 2:04 8:50:49 5.59% 214
Be sure to read your instructor's class announcements every time you log
in, or frequently on the class webpage, for important information which may
be present. You are responsible for the content of these announcements. To
be certain to never miss this information, and so you can submit your
projects, you must execute the command source ~<instacctID>/setup
which will cause these announcements to be displayed whenever you log in
(where <instracctID> must be replaced by the name of your
instructor's class posting account). This only needs to be done once for
the semester, and the announcements will be shown every time you log on
afterwards.