// if user enters one number
// program should determine if that number is a prime

if (argc == 2)
{  
   if (a[argc] == 1)
   {  
       counter++;
       cout<<"This is a prime number."<<endl;  
   }
   else
   cout<<"This is not a prime number."<<endl;
}

#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <stdlib.h>

using namespace std;


int main(int argc, char *argv[])
{
   const unsigned long arraySize = 1000000;
   bool a[arraySize];
   unsigned long num1;
   unsigned long num2;
   unsigned long num3;
   unsigned long counter = 0;
   unsigned long primes = 0;
   char z;
   unsigned long answer = 0;
  

cout<<"This program is programming assignemnt #5."<<endl;
cout<<"THE SIEVE OF ERATOSTHENES."<<endl;
cout<<"By Marley Walsh of CSCI 111."<<endl;


//Initializing elements to 1
        
for (int i = 0; i < arraySize; i++)            
{
   a[i] = 1;
}      
// For array subscript 2, all elements beyond 2 in the array that
// are multiples of 2 will be set to zero; for array subscript 3,
// all elements beyond 3 in the array that
// are multiples of 3 will be set to zero


for (int i = 2; i * i < arraySize; i++)
{
    if (a[i])
       for (int j = i + i; j < arraySize; j += i)
          a[j] = 0;
}  
        
// if user enters one number
// program should determine if that number is a prime

if (argc == 2)
{  
   if (a[argc] == 1)
   {  
       counter++;
       cout<<"This is a prime number."<<endl;  
   }
   else
   cout<<"This is not a prime number."<<endl;
}

// if user enters 2 numbers
// program, should calculate the prime numbers
// between the two numbers

if (argc == 3)
   {
        
   }


// if user enters more than 3 numbers or 0 numbers
// program should output useful information
// and title and author

if ((argc > 4) || (argc == 1))
{
cout<<"This is Programming Assignment #5"<<endl;
cout<<"THE SIEVE OF ERATOSTHENES"<<endl;
cout<<"by Jeremy Rice"<<endl;
cout<<endl;
cout<<"Usage:"<<endl;
cout<<"\tprime num1 - determines if num1 is a prime"<<endl;
cout<<"\tprime num1 num2 - displays primes between numbers."<<endl;
}
return EXIT_SUCCESS;
}

int numb;
numb=atoi(argv[i]);
printf("%d\n",numb);

#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <stdlib.h>

using namespace std;
const unsigned W = 10;

int main(int argc, char *argv[])
{
   const unsigned long arraySize = 1000000;
   bool a[arraySize];
   unsigned long num1;
   unsigned long num2;
   unsigned long num3;
   unsigned long counter = 0;
   unsigned long primes = 0;
   char z;
   unsigned long answer = 0;
  
//Initializing elements to 1
        
for (int i = 0; i < arraySize; i++)            
{
   a[i] = 1;
}      
// For array subscript 2, all elements beyond 2 in the array that
// are multiples of 2 will be set to zero; for array subscript 3,
// all elements beyond 3 in the array that
// are multiples of 3 will be set to zero


for (int i = 2; i * i < arraySize; i++)
{
    if (a[i])
       for (int j = i + i; j < arraySize; j += i)
          a[j] = 0;
}
// if user enters more than 3 numbers or 0 numbers
// program should output useful information
// and title and author

if ((argc > 4) || (argc == 1))
{
cout<<"This is Programming Assignment #5"<<endl;
cout<<"THE SIEVE OF ERATOSTHENES"<<endl;
cout<<"by Jeremy Rice"<<endl;
cout<<endl;
cout<<"Usage:"<<endl;
cout<<"\tprime num1 - determines if num1 is a prime"<<endl;
cout<<"\tprime num1 num2 - displays primes between numbers."<<endl;
}



num1 = atoi(argv[1]);
num2 = atoi(argv[2]);
num3 = num1;
// if user enters one number
// program should determine if that number is a prime

if ((argc > 1) && (argc < 3))
{
   if (a[num1] == 1)
   cout<<num1<<" is a prime number."<<endl;
   else
   cout<<num1<<" is not a prime number."<<endl;
}

// if user enters 2 numbers
// program, should calculate the prime numbers
// between the two numbers

if (argc == 3)
   for (int i = num1; num1 < num2; num1++)

    if (num1 < num2)
    if (a[num1] == 1)
     {
      counter++;
      cout<<setw(W)<<num1;
     }
       else if
        (a[num1] == 0)
     {
         cout<<"";
     }  
        else
          cout<<"num1 must be lower than num2."<<endl;          
if (num1 > num2)
{
cout<<"Error: Invalid user specified number."<<endl;
return 0;
}
cout<<endl;
cout<<"There are "<<counter<<" primes between "<<num3<<" and "<<num1<<endl;
return EXIT_SUCCESS;
}

// if user enters one number
// program should determine if that number is a prime

if ((argc > 1) && (argc < 3))
{
   if (a[num1] == 1)
   cout<<num1<<" is a prime number."<<endl;
   else
   cout<<num1<<" is not a prime number."<<endl;
}

// if user enters 2 numbers
// program, should calculate the prime numbers
// between the two numbers

if (argc == 3)
   for (int i = num1; num1 < num2; num1++)

    if (num1 < num2)
    if (a[num1] == 1)
     {
      counter++;
      cout<<setw(W)<<num1;
     }
       else if
        (a[num1] == 0)
     {
         cout<<"";
     }  
        else
          cout<<"num1 must be lower than num2."<<endl;          
if (num1 > num2)
{
cout<<"Error: Invalid user specified number."<<endl;
return 0;
}
cout<<endl;
cout<<"There are "<<counter<<" primes between "<<num3<<" and "<<num1<<endl;

cout<<endl;
cout<<"There are "<<counter<<" primes between "<<num3<<" and "<<num1<<endl;