CS 2213/2211  Advanced Programming  Spring 2005  Recitation 1  Introduction to C, Unix, and vi     Week 1: Jan 18-20  Due (on time): 2005-01-25  23:59:59  Due (late):        2005-01-30  23:59:59

Recitation 1 should be submitted following directions at: submissions with deadlines 2005-01-25  23:59:59 (that's Tuesday, 25 January 2005, 11:59:59 pm) for full credit. 2005-01-30  23:59:59 (that's Sunday, 30 January 2005, 11:59:59 pm) for 75% credit.

/* dice: Gather statistics about rolling
 * two dice.  A Monte Carlo simulation using
 * the random number generator rand()
*/
#include <stdio.h>   /* for the input/output */
#include <stdlib.h>  /* for rand and srand */
#include <time.h>    /* for time */

/* function prototypes */
void initarray(int d[]);
void printarray(int d[]);
void printstar(int n);
void fancyprint(int d[]);
int roll(void);
/* global variable */
int numrolls;

int main(void) {

   int d[13]; /* 2-12 hold num of rolls */
   int i;     /* loop variable */
   int starttime = time(NULL); /* clock time */
   srand((long)starttime); /* initialize RNG */
   printf("Enter # of rolls ---> ");
   scanf("%i", &numrolls); /* need & on var */
   initarray(d);
   printf("Total rolls: %1d\n\n", numrolls);
   for (i = 0; i < numrolls; i++) /* simul. */
      d[roll() + roll()]++;
   printarray(d);
   fancyprint(d);
   printf("Elapsed time: %ld seconds\n",
      time(NULL) - starttime);
   return 0;
}

/* initarray: initialize statistic array */
void initarray(int d[]) {
   int i;
   for (i = 2; i < 13; i++)
      d[i] = 0;
}

/* printarray: print each num of rolls */
void printarray(int d[]) {
   int i;
   double e[] = {0, 0,  /* frequencies */
      1.0/36.0, 2.0/36.0, 3.0/36.0, 4.0/36.0,
      5.0/36.0, 6.0/36.0, 5.0/36.0, 4.0/36.0,
      3.0/36.0, 2.0/36.0, 1.0/36.0};
   printf("Sum  Times   Frequency");
   printf("      Exact    Diff\n\n");
   for (i = 2; i < 13; i++)
      printf("%2d %7d %11.7f %10.7f %8.4f\n",
        i,
        d[i],
        (double)d[i]/numrolls*100.0,
        e[i]*100.0,
        ((double)(d[i]) -
           e[i]*numrolls)/numrolls*100.0);
}

/* printstar: print n stars */
void printstar(int n) {
   while (n > 0) {
      printf("*");
      n--;
   }
}

/* fancyprint: print bar graph */
void fancyprint(int d[]) {
   int i;
   printf("\n");
   for (i = 2; i < 13; i++) {
      printf("Sum:%3d |", i);
      printstar(300*d[i]/numrolls);
      printf("\n");
   }
   printf("\n");
}

/* roll: simulate rolling a die */
int roll(void) {
   return (int) (6.0*(rand()/(double)RAND_MAX)
      + 1.0);
}

1. Study the lecture notes about Unix: Unix Basics.
2. Using the command line in a terminal window, create a new directory for this assignment, say rec1.
3. Put the program above into your own file dice.c. (Either just copy and paste from the listing above, or use this copy: dice.c.)
4. Study the writeup: lint and make. Create a Makefile for the program dice.c.
5. Use this Makefile and the make utility to check the program using the lint utility. (You will need to run lint on the Sun system.)
6. Use the same Makefile to compile and execute this program, using either cc or gcc as the compiler. When you execute, you should enter a fairly large number for the number of rolls, such as 1000000.
7. Study the dice program and how it works by looking at the presentation of a line-by-line comparison between C and Java for this program: Dice Program in C and Java.
8. Study the writeup about the vi editor: vi Editor. Use vi to make the following changes to the program:
   1. Change the program so that it records the results of rolling three dice instead of two.
   2. You will need to make various modifications to the program, calling the new program: dice3.c. In particular, the possible sums will range from 3 to 18, so you need to change arrays and for loops. The actual frequencies with which the sums from 3 to 18 come up are given in the following table:

      
         double e[] = {0, 0, 0,  /* array of frequencies */
             1.0/216.0,  3.0/216.0,  6.0/216.0, 10.0/216.0,
            15.0/216.0, 21.0/216.0, 25.0/216.0, 27.0/216.0,
            27.0/216.0, 25.0/216.0, 21.0/216.0, 15.0/216.0,
            10.0/216.0,  6.0/216.0,  3.0/216.0,  1.0/216.0};
      

   3. Repeat the make, lint, compile, and run as with the original program.

9. Make up a single text file for submission, as described in the next section.

Contents of email submission for Recitation 1: Last Name, First Name; Course Number; Recitation Number. a. Your Makefile for the program dice.c. b. Result of running lint for the same program, using the Makefile. c. Result of running the compiled program, using the Makefile. Enter a fairly large number for the number of rolls, such as 1000000. d. C source code for the rewritten program to handle the sum of the spots of three rolls, now called dice3.c. e. Result of running lint for this program, using a slightly altered Makefile. f. Result of running the compiled program, using the slightly altered Makefile. Enter a fairly large number for the number of rolls, such as 1000000.