PROGRAM 59

Object

Write a program to print all prime numbers up till a specified range.

Algorithm

1. Declare integer variables a, b and num.
2. Read num.
3. Set a = 2.
4. Repeat WHILE a <= num
   • Set b = 2.
   • Repeat WHILE b < a
     • IF a mod b = 0, then
       • Break out of loop.
     • ELSE
       • b++.
     • [End of IF-ELSE structure.]
   • [End of inner WHILE loop.]
   • IF a = b, then
     • Write a
   • [End of IF structure.]
   • a++.
   • [End of outer WHILE loop.]
5. Exit.

Flowchart

C++ Source Code

// program 59
#include<iostream>
using namespace std;

int main()
{
  int a, b, num;

  cout << "Enter the number: ";
  cin >> num;
  a = 2;

  while (a <= num)
  {
    b = 2;
    while (b < a)
    {
      if (a % b == 0)
        break;
      else
        b++;
    }

    if (a == b)
      cout << a << "\t";
    a++;
  }
  return 0;
}

C Source Code

/*program 59*/
#include<stdio.h>

int main()
{
  int a, b, num;

  printf("Enter the number: ");
  scanf("%d", &num);
  a = 2;
  while(a<=num)
     {
     b = 2;
     while(b<a)
	{
	if(a%b==0)
	  break;
	else
	  b++;
	}
     if(a==b)
       printf("%d\t", a);
     a++;
     }
  return 0;
}

Output

Enter the number: 100
2       3       5       7       11      13      17      19      23      29      31      37      41      43      47     53       59      61      67      71      73      79      83      89      97