After a long absence from these boards and some more programming under my belt, I have finnally dived into C because I have my first college C class this semester. I just finished writing my first C program other than the classic "hello world". It is a program that asks for user input of an integer and decided whether or not the integer is a prime number. This program is no where near efficient and I plan on narrowing down its testing phase to only include numbers that could possibly be a prime (i.e. nothing higer than the root of the input) I would like to write a program that will test this program for each interger up to a stopping point. Also any other efficiency suggestions would be apprecieated.
/****************************************************
*
* Programmer and Purdue Email Address:
* 1.Chris Cadwallader
*
* Program Description: This program asks for user
* input of an integer an outputs whether the
* integer is a prime number or not.
*
*
***************************************************/
#include <stdio.h>
int main()
{
/* Local Definitions */
int testval; // Integer to be tested
int denom; // Denominator used in calculations
int testresult; // Calculation result
int counter; // Loop iteration counter
/* Statements */
/* Requesting an integer */
printf("\n\nWelcome to the Prime number testing program.");
printf("\n\nPlease Enter an integer to be tested: ");
scanf("%d", &testval);
/* Verifying that the input is an integer greater than 1 */
while (testval < 1)
{
printf("\nThe test value cannot be smaller than 1.\n\n");
printf("\n\nPlease enter an integer to be tested: ");
scanf("%d", &testval);
} /* while */
if (testval == 2)
printf("The value entered is a prime number.\n\n");
else
{
denom = 2;
testresult = testval % denom;
counter = 1;
/* Testing integer for prime status */
while (denom < testval)
{
testresult = testval % denom;
if (testresult == 0)
denom = testval;
else
counter++;
denom++;
} /* while */
if (testresult != 0)
printf("The value entered is a prime number.\n\n");
else
printf("The value entered is not a prime number.\n\n");
} /* else */
printf("This program looped %d times to complete the problem.\n\n",counter);
return 0;
} /* main */
thanks
ps..... my posts seem to have dissappeared.... now I only have 2..... thats strange.