Sample Programs
			       Thursday 7/11/02

Example #1
----------
// This program computes all the primes from 2 to 100.
#include <iostream.h>

int main() {

  const int num = 100;

  int counter = 2;
  int check;
  bool isprime;

  cout << "The prime numbers from 2 to " << num << " are :\n";
  while (counter <= num) {
    
    isprime = true;
    check = 2;
    while (check < counter) {
  
      if (counter%check==0) {
        isprime = false;
        check = counter;
      }
      check = check + 1;
    }   
    if (isprime)
      cout << counter << " ";

    counter = counter + 1;
  }

  return 0;
} 

Example #2
----------
//Computes the average of all the test grades entered by user.
#include <iostream.h>
void main() {
  int grade = 0;
  int sum = 0;
  int numtests = -1;
  double average;
  
  cout << "Enter all of your grades, followed by a -1 to signify you are done.\n";

  do {
    sum = sum + grade;
    numtests++;
    cin >> grade;
  } while (grade !=-1);

  if (numtests==0)
    cout << "Sorry no grades entered to average.\n";
  else {
    average = double(sum)/numtests;
    cout << "The average of your grades was " << average << endl;
  }    
}

Example #3
----------
#include <fstream.h>
#include <iostream.h>

//Function prototypes.
char askchar();
int countchar(char);

 
void main() {

  char search1, search2, search3;

  cout << "This program	computes the number of occurances of a three\n";
  cout << "characters in the dictionary.\n";
  cout << "To quit, enter a #.\n";

// Uses function call to determine the character entered by user, and how many
// of that character are in the dictionary.
  search1 = askchar();
  int count1 = countchar(search1); 
  cout << "The number of " << search1 << "'s in the dictionary is " << count1 << endl;

// The two following blocks of code do exactly what the first does.
  search2 = askchar();
  int count2 = countchar(search2); 
  cout << "The number of " << search2 << "'s in the dictionary is " << count2 << endl;
 
  search3 = askchar();
  int count3 = countchar(search3); 
  cout << "The number of " << search3 << "'s in the dictionary is " << count3 << endl;

}


// This function asks the user for a character, reads it in and returns that char.
char askchar() {
  char c;
  cout << "Enter the first character you want to search for.\n";
  cin >> c;
  return c;
}

// This function counts the number of occurances of the character c passed into it
// in the dictionary.
int countchar(char c) {

  char dummy;
  int count = 0;

  ifstream fin("input.dat");

  while (fin >> dummy) {
    if (dummy==c)
      count++;
  }
  return count;
}


Example #4
----------
#include <fstream.h>
#include <iostream.h>

char askchar();
int countchar(char);
void oneiter();
 
void main() {

  char search1, search2, search3;
  int i;

  cout << "This program	computes the number of occurances of a three\n";
  cout << "characters in the dictionary.\n";
  cout << "To quit, enter a #.\n";

  for (i=0;i<3;i++)
    oneiter();

}

char askchar() {
  char c;
  cout << "Enter the first character you want to search for.\n";
  cin >> c;
  return c;
}

int countchar(char c) {

  char dummy;
  int count = 0;

  ifstream fin("input.dat");

  while (fin >> dummy) {
    if (dummy==c)
      count++;
  }
  return count;
}

// This is a void function that executes one block of code from example #4
void oneiter() {
  
  char c = askchar();
  int count = countchar(c); 
  cout << "The number of " << c << "'s in the dictionary is " << count << endl;

}