CS/ECE 354 Machine Organization and Programming Fall 2008 Section 1 Instructor Mark D. Hill TAs Mark Liu & Somayeh Sardashti

Homework 1 // Due at Friday, September 26, before 5pm

Send e-mail questions to Mark Liu, mliu@cs.wisc.edu

Collaboration Policy

For this assignment, you may work in pairs (2 people). All students (whether working in a pair or not) must individually turn in the assignment by individually running the handin program. Therefore, 2 copies of the assignment will be turned in for those working as a pair. The grader will choose to grade only one copy of a pair's work, and assign the same score to both students.

If working in a pair, the names of BOTH students must appear at the top of the turned in assignment.

Program

The purpose of this program is to write a C program, gaining the experience of working in a non-object oriented language.

Program Statement

Write a C program that defines a range of integer values with command line arguments. There are two command line arguments that are both single digit integers that make up a range. The program determines whether or not each value in your range is coprime with each of the values in the range 2-9. These values are then printed out in the format of the examples shown below.

Two numbers are coprime (a.k.a. relatively prime) if and only if they have no common factors besides 1. Equivilently, their greatest common divisor is 1. For example, 4 and 9 are coprime but 4 and 6 are not because they share the divisor 2.

Command line arguments are used to tell the program lower and upper bounds to specify the range of integers to include.

Here are several examples of program execution, where the command line and user's input is given in boldface. These examples presume that the executable is called coprime. Read these examples carefully, as they define what the program must do for edge cases, as well as for error cases.

% coprime 3 6
        2 3 4 5 6 7 8 9
3       Y N Y Y N Y Y N
4       N Y N Y N Y N Y
5       Y Y Y N Y Y Y Y
6       N N N Y N Y N N

The following examples illustrate what the program does with unusual, unexpected, and bad command lines. The italics header over each describes the difficulty within the command line.

% coprime
Invalid command line. Both lower and upper bounds must be
greater than 1 and less than 10.  Usage:
coprime <lower> <upper>

% coprime X 5
Invalid command line. Both lower and upper bounds must be
greater than 1 and less than 10.  Usage:
coprime <lower> <upper>

% coprime 6 -3
Invalid command line. Both lower and upper bounds must be
greater than 1 and less than 10.  Usage:
coprime <lower> <upper>

% coprime 5 4

Organization and Requirements

1. Declare and use an array of 10 characters. Please declare this array statically. Define the preprocessor macro:

   
   #define ARRAYSIZE 10
   
   

   and use this constant value as the array's size in the declaration:

   
   char array[ARRAYSIZE];
   
   

   This (single, static) array is used (and re-used) to hold the results for each of the integers in the range. These results should be of the form Y or N.
2. Use the C function atoi() to convert the command line arguments into an integer representations. Where this string is not an integer, use the value 0 (as returned from atoi()). This utility function is in stdlib.h.
3. Organize your code such that it uses the following functions:
   
   void getCoprimes(char ar[], int firstindex, int lastindex, int numerator)
   This function calculates whether or not each pair is coprime and places them into the array. At ar[firstindex], it places the result of whether or not numerator and firstindex are coprime. At ar[firstindex+1], it places the result of whether or not numerator and (firstindex+1) are coprime, etc.
   
   void printArray(char ar[], int firstindex, int lastindex)
   This function prints the results Y/N that are the array elements, nicely spaced. The parameter firstindex gives the array index of the first array element to print, and lastindex gives the array index of the last array element to print.
   
   
4. Your program must follow style guidelines as given in See Style Guidelines.

   Also include a comment at the top of the source code with your name (and your partner's name, if working in a pair).

   See Guidelines for Programs to see an indication of point allocation for program grading.

5. Name your source code program coprime.c, and place the entire program into this file. This single file is what will be turned in. It must have exactly this name to make the lab-supported handin program work.
6. Organize your code such that the only exit point(s) are in main().
7. Your program is to operate the same as the examples given above. Use the same formatting, strings, and messages as given in the samples.
8. Use the Unix machines assigned for this class! A penalty will be imposed for any program that was obviously editted on a Windows machine and transferred to the Unix machines for turning in.
9. Yes, this program could be implemented without an array, and without the requested functions. However, follow the instructions, as this assignment is meant to force you to use an array (and pointers), as well as pass parameters. There will be a severe score deduction for a solution that does not follow the directions.

About Copying Code and Academic Misconduct

For almost any C program that does something useful, someone has already written this program and further, has posted it for others to use. This program does not do anything useful, and is not likely posted anywhere. Still, it is academic misconduct for you to copy or use some or all of a program that has been written by someone else.

The penalty for academic misconduct on this assignment will be a failing grade in the course. This penalty is significantly more harsh than if you simply do not do the assignment.

You will gain much more by doing the assignment than by copying, possibly modifying, and turning in someone else's effort.

Notes

1. To compile a C program, use a C compiler. cc run on our Centos Linux machines is expected for this assignment. If the name of the C source code program were myprogram.c, then the Unix command
   cc myprogram.c
   will compile this program, placing the executable program in the file a.out. Note that this command (given in this manner) must be executed while your current working directory (often abbreviated cwd) is the one containing the C source code file. To place the executable in a file other than a.out, add another option and argument to the command line:
   cc myprogram.c -o executablename
   To run this executable simply type into the command line:
   ./executablename arg1 arg2
   
   (Be forewarned: If you use another C compiler, for example on your own computer, and its implementation allows code that causes warnings or errors when compiled as expected, you will lose points.)
2. This program requires the use of command-line arguments. Look at Kernighan and Ritchie (2nd edition) section 5.10 for an excellent explanation of how they work. The online class notes also contain an explanation. Essentially, argc is a count of the number of white-space delimited strings that were used in the command. For this program (when correctly used) there will be 3. Note that the first argument is the name of the program. argv is a pointer to an array of pointers to characters (strings), where each string is one of the white-space delimited arguments.
3. The shell (which processes Unix commands) assigns functionality to some characters, and handles them differently. Therefore, the command-line arguments can have unexpected values (depending on which shell the user is using). Your program is expected to correctly handle any alphanumeric character within the command-line arguments.
4. A note to those few students who do not read carefully: the machine route66 is NOT one of the instructional machines assigned for use by this class. In fact, it is a different platform, and the C compiler is linked differently.

Handing In the Program

We will use the lab-supported handin program. If you wish to modify your path to make the command shorter, follow the instructions on the CSL web page Electronic Hand In System.

*Do not turn this program in until noon on Wednesday, September 24th*

Your C source code must be in a file named coprime.c. Turn in your program by running the lab-supported handin program.

  /s/handin/bin/handin -c cs354-1 -a a1 -d .