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Quadratic Formula Program


 
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# 1  
Old 02-07-2002
Quadratic Formula Program

I have a question about the program I am making. I finished it, compiled it, and there were no errors. Now when I run it, the comand prompt comes up and there are just 1's and 0's that keep looping over and over again. The program is listed before. If anyone has any suggestions I would greatly appreciate it.
Code:
/* *************************************************

Purpose:      Solve for the roots of the quadratic equation,
                       y = a x^2 + b x + c
                 by means of the quadratic formula,
                 root = (-b +or- sqrt(b^2 -4. a c))/(2. a)

Variables:    a, b, c + Real coefficients of quadratic equation.
                 d = Discriminant
                 root1, root2  = Real roots or real part of complex roots.
                 root1i,root2i = Imaginary part of complex roots.
Input:        Values of coefficients in file 167w02cp1c.dat
Output:       Tabulated values of coefficients and roots, with
                 proper heading and captions, in the UNIX xterm    window.

************************************************** */

#include <stdio.h>      /* Access input/output functions */
#include <math.h>       /* Access math functions */

void main(void)
{
/* Float all variables */

         double a, b, c, d, root1, root2;
         double root1i,root2i;

         FILE *fp;

         fp = fopen ("167w02cp1c.dat","r");       /* Open input file */
         if (fp==NULL)                       /* Test for file not open */
{                                                /* Terminate the program */
                 puts("\nData file 167w02cp1c.dat has failed to open.");
                 puts("\nProgram cp1.c is terminated.\n");
                 return;
}

puts("\n                 Class goes here");
puts("\n                     2002");
puts("\n                    Name goes here");
puts("\n                   Problem No. 1");
puts("\n                 Roots of Quadratic Equations");
printf("\n      a         b         c       root1   ");
printf("  Root2");
printf("\n -------------------------------------------------");
printf(" ----------------------------------------");

while (! feof(fp))                             /* Start of Loop */
{
   fscanf (fp,"%1f%*c%1f%*c%1f",&a,&b,&c);     /* Input Values */

             if (feof(fp))                   /* Looks for end of file */
                      {
                      puts("\n End of Data. Program cp1 complete,");
                      break;
}

if (a==0. || b==0. && c==0.)    /* Check for invalid data */
        {
        printf("\n%10.3f%10.3f%10.3f    invalid data",a,b,c);
        }
        else
                d = ((b*b)-(4*a*c));    /* Compute the Discriminant */

/* Compute roots for when the discriminant is positive */

        if (d>1.0*pow(10,-6))
        {

        root1 = ((-b)+pow(d,0.5))/(2*a);
        root2 = ((-b)-pow(d,0.5))/(2*a);

        printf("\n%10.3f%10.3f%10.3f%13.3f%13.3f",
                 a, b, c, root1, root2);
                 /* Print Values */
        }

/* Compute roots for when the discriminant is negative */

else if (d<-1.0*pow(10,-6))
{

        root1 = -b/(2.*a); root2 = root1;

        root1i = sqrt(-d)/(2.*a);
        root2i = -root1i;

        printf("\n%10.3f%10.3f%10.3f%8.3f%8.3f%8.3f%8.3fi",
           a, b, c, root1,root1i,root2,root2i);        /* Print Values */
        }

else
        {
         root1 = (-b)/(2*a);
         root2 = root1;

         printf("\n%10.3f%10.3f%10.3f%13.3f%13.3f",
                a,b,c,root1,root2);
}
}
}               /* End While Loop */

added code tags for readability --oombera

Last edited by oombera; 02-20-2004 at 02:38 PM..
# 2  
Old 02-08-2002
Re: Quadratic Formula Program

We are not allowed to do your schoolwork for you. But you have one nasty hard-to-find bug that may not be your fault:
Quote:
Originally posted by zeek
fscanf (fp,"%1f%*c%1f%*c%1f",&a,&b,&c);
That can't be right. I think those one's should be letter l's. A letter-l says that a, b, and c are doubles, which they are. A one says that field is a single character wide.

Always make sure that you are using a font that lets you see the difference between 1 and l. Ditto for O and 0.
# 3  
Old 02-22-2002
Good job everyone. This is an example of the posting doing his/her own work and being stuck on a tricky syntax or font issue. Posting homework problems are clearly frowned upon, but in this case considerable effort and work was put into the problem and the confusion between a "1" and an "I" was not really part of the assignment.

Perderabo did a stellar job in the way he answered this post Smilie

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